Step 1: Tools and Supplies
Disclaimer: this instructable involves, among other things, messing around with wires in your wall. I am not an electrician. I've done a lot of light fixtures and ceiling fans on my own, but I never have anything inspected by a professional. Though everything functions as intended upon completion, I might have done something incorrectly. Feel free to correct me, or add tips for other people in the comments below.
Step 2: Preparation
There was a slight texture to the plastic, so the paint shows this texture, but I don't mind because it'll be mostly hidden from view. If I wanted a very glossy look, it would have been easy to sand it down. Any scratches in the paint during installation I touched up with a black Sharpie. Cheap, but again, it will be mostly hidden from view.
Also for preparation, before removing the TV from its mount, I taped off where the corners of the TV were on the wall. This allowed me to quickly see where the edges of the TV were, without having to make a lot more measurements once the TV was removed. Not seen in the photos, I also marked where the hooks on the TV were located on the mount itself (low-tech method of dabbing my finger in the accumulated dust). With these reference points, it was easy to locate the best spot to place the media box, so the HDMI cable would run directly into the desired input port on the back of the TV from the wall.
I also marked the best spot for the power outlet. I knew my TV tilted forward, and the power plug needed a few inches of space once plugged in, so I located it above the bracket where there would be enough space. A recessed power outlet could also be used, if more space is needed for the plug.
Step 3: When Old Meets New
I was lucky enough to have a power outlet located below the TV. My plan was to install a new outlet directly above it, pull romex cable through to the preexisting outlet, and wire it to that (is that 'in series'?). I consulted with people who I believe know more than me on the subject, and they said this would be fine.
I removed the preexisting outlet from the wall, and familiarized myself with the wiring. This particular outlet has a wall switch that controls the upper outlet (indicated by a red wire, this outlet/switch is used for a lamp), and the lower outlet has constant power (indicated by the usual black wire). I wanted to connect my new outlet to the constant power source, so the wall switch didn't turn my TV off. I also removed one of the access hole covers in the top of the metal box that the outlet was mounted in, by prying it off with a screwdriver.
I marked my location for the new outlet using the new "old construction power box" (the white one in the pic on step 1) as a guide for size, and cut the hole. Save the piece you cut out, don't let it fall in the wall, it's always good to have on hand in case you make a mistake and need to make a patch on the wall. Then, using the fish tape, I pulled the romex cable through the wall, through the access hole in the top of the box, being sure to pull some excess through to keep it from falling back into the wall once cut.
I cut the bottom of the cable, stripped the insulation and paper lining (the blade slits and cuts the outer insulation easily), separated the 3 wires (black, white, bare ground), and stripped off about 1.5" of insulation from each one using the wire cutters (wire strippers would work too). Using the needle nose pliers, I bent a hook shape into each one, so they could easily attach to the screws on the outlet.
I attached each wire to their corresponding locations on the lower portion of the outlet. The old black wire was pushed into a hole in the outlet, so I wrapped the new black wire on the screw next to that hole, and tightened it. I did the same with the white wire and ground (see pic for details). I tightened each screw, then I shoved it all back in the metal box, screwed the old outlet back into place, and screwed the face plate back on.
Step 4: Power!
I cut the romex to length, and stripped off the insulation and separated the wires just as before. Again, I bent the wires with the needle nose pliers to easily attach to the screws. I attached each wire to the correct location, and tightened the screws. I shoved the new outlet into its box, attached it with the two screws that came in the package, and attached the new face plate with the screw that came in its package.
I had my son watch for any sparks/flames/sounds ("yell as loud as you can if you see/hear anything") and I ran downstairs to flip the breaker back on. The breaker didn't trip, and my son didn't scream, so that was good. I went back upstairs, and tested each outlet with the lamp. Both new outlets worked, and didn't shut off when I flipped the wall switch. Both the old outlets still worked, and the upper one turned off with the wall switch, as desired. Huzzah!
Step 5: Some Holes
After marking my location, I held up the new "old construction low voltage box" and marked the 4 holes for the cut guide. I cut the hole. I then attached the voltage box by placing it in the hole, verifying it fit, and tightened the two screws. For the lower media box, I wanted it to be located as close to center (in relation to the TV) as possible, and the same height as the power outlets and surround sound outlet. Careful not to place it in a location that would cause the cable to cross a stud (not as close to center as I would have hoped, but still good), I marked its location and did the same process of marking holes and cutting. I installed the voltage box there in the same manner as before.
By this point I'm pretty hungry and ready to finish, so I don't have as many pics, but they're not really needed. I also encountered an unforeseen problem, which I'll discuss at the end.
Using the fish tape, I pulled the HDMI cable through. I attached the media boxes, mounted the TV, and verified that the HDMI cable did indeed line up to the media box. Prior to mounting the TV, I wound up a few coils of the power cable, and zip-tied it in place so the excess wouldn't hang below the TV. I tilted the TV forward (the desired final resting position), and plugged the power cable in the new outlet. It works, more success!
Step 6: Unforeseen Problem
When cutting the hole for my lower media box, I ran right into this. In my hungry and frustrated state, I contemplated cutting the metal for a moment, but decided against it. I was able to move my hole over a little without causing additional damage, but the strap covered about half the hole. I figured I could make it work. I had to trim a bit off one of the the voltage box tabs, but it still fit nicely. Also, the back of the media box protrudes a bit (it looks as if it's intended to help organize multiple cables), so I trimmed that down as well. The HDMI cable also has thick insulation, and has a webbed sheath, so I was not worried about it coming in contact with the metal strap, which didn't have a sharp edge. All said and done, it worked great!
But prior to be being "all said and done", I was trying to guide the fish tape from the upper hole to the lower hole. Somehow, I'm really not sure, I must have hooked the power cable that runs horizontally in the wall. The little bent portion on the end of the fish tape is pretty tight, so I'm not sure how it easily hooked on the power cable. After trying all sorts of maneuvers, and after much frustration, I resolved to cut the fish tape and leave about 3' in the wall. Oh well. With the end of the fish tape now a sharp, pointed nub, I no longer had to worry about getting it caught on anything, but it also made it useless for attaching wires that need fishing. I bent it into a horrible hook, and that worked fine.
But taking into account how many things I've done for the first time, with the surround sound, media boxes, and power outlet, I'm surprised this was the only problem I ran into. I'm thankful for that!