All you need is the RockBand 1 (I haven't tried with the RockBand 2 drums yet) drums, a screwdriver, and possibly the knowledge of how to make a simple splice.
Here is a video of me playing with them (for the first time)
Step 1: Dismantling the Drum Set
-First, you need to take off the rubber heads you would usually hit. This is very easy, all you need to to is rip them off from the side (this won't hurt anything)
-Next you need to unscrew all the screws on the backside of the RockBand drums, and basically every screw you think will help take it apart
-After you have taken all the screws out, if the plastic pieces don't separate easily, there are also some screws under the foam inside of the middle 2 drum
You should be able to take the yellow and blue wires out, but the green and red should be stuck in between some plastic
Step 2: The Wires
At the end of this step, you want all the wire from inside of the RockBand drum set out. You should be able to take all of the wires out besides the red and green. You will either need to cut the plastic around the wire, or cut both of the wires and splice them after. If you don't know how to splice a wire, you basically take the covering off of the two wires, twist the white to white, and colored to colored, and after, you can cover them separately with electrical tape to make sure they don't touch/short circuit (If you don't like my explanation of splicing, maybe you can find another intractable that explains it better). Then, take all of the wires out. you should have:
-One control circuit
-4 colored wires with sensors on the end
-1 input for the bass pedal
-1 USB wire
Step 3: Attaching to the Real Drum Set
First, you rest the controller/circuit board part on the bass drum in a position where all of the sensors can reach the drums. The hit sensors already have tape on them when you remove them from the RockBand set, so you don't even really need tape. I recommend taping them to plastic ring inserts if you have them. The wires are only long enough to put them on your snare and toms, but if you want to (I haven't done this yet so I'm not ure how well it may work) you can cut the wires and splice a longer piece of wire in between them so the yellow can fit the hi hat (i know this works), and maybe the green can attach to the ride, and the blue to the crash maybe. It's the vibration from hitting the drum head triggers the sensor which is translated as a "hit".
Step 4: The Bass Pedal
The bass pedal is attached to the rest of the controller through the normal bass pedal port. The easiest way to use the bass pedal is to take your usual pedal aways and use your RockBand pedal or just place them next to each other. The harder way (which is purely theoretical because I have not attempted this) involves taking apart the RockBand pedal. On the inside of the RockBand bass pedal is a button activated by magnets that is usually in the black part of the pedal. Underneath the part your place your foot on is a small magnet that triggers the magnetic button when they get close enough by you pressing down on the pedal.
UPDATE: After I published this instructable, I saw a good instructable on making the bass pedal work, you can view it here.
My idea is that you can place the piece next to (or in between for double bass) the batter head and tape/glue a magnet on side of the batter head(s). my other idea is keep the trigger under the pedal and a magnet on the underside of the pedal. I haven't tried either of those ideas, nor do I plan on trying them, but I thought I would put them out there incase anyone wanted to try them, and if you do, please leave a comment and tell my how it went!
Step 5: Play!
This cheap way to play RockBand with real drums isn't perfect, but it IS a whole lot of fun!
YOU WILL DEFINITELY WANT TO RECALIBRATE YOUR DRUM SET IN THE SETTINGS.
If your TV has a headphone port, or you can somehow get the sound into headphones would definitely be ideal. There are plenty of guides on how to do that, but I still havn't yet so I'll leave that up to you, but its still fun either way. One problem I have had is that some times I'd hit blue and it would shake the whole bass drum and activate yellow too, and since the floor tom is so large, it sometimes triggers green twice. Also, be careful not to hit the sensors, it might be a good idea to use the foam from inside the RB drums to protect the sensors. Have fun playing with your new RockBand drum set!