At one point I replaced a passenger side mirror, which broke due to some water/ice build up. To do so, one has to remove the door.
"Sure!" I thought. "I'll figure out how to do that." I assumed the door slipped over the plastic thing that goes around the door handle. I was wrong, but I had to break it to figure this out.
Step 1: Unscrew the Assebly
Oh! There's a screw! Um. Now I know.
There's a small panel just above the handle. You'll need a small screw driver to pry it open. After doing so, there's a phillips head screw to unscrew, and the whole thing comes off.
Learn from my pain.
Step 2: Unscrew the Door Lock
There are two small screws that hold the door lock and wires onto the assembly. Remove them.
Step 3: Replace and Repair
Screw the lock mechanism into the new assembly. Put it back in the door, and reattached the main screw. Close up the panel, and you're done!