How To: Fix your (rear) door lock.
1. Remove your door panel: There are 2 screws in the handle assembly (one behind the door handle, one behind the lock) and 2 screws in the handle.
Use an upholstery remover to take off the window crank (if you have crank windows). Note that there is a cotter pin holding the crank in place. You have to pull it off before the handle comes free.
Once the fixtures are free, the door panel can be pulled off. Don't worry about giving it some force, the whole thing is just snapped on.
2. Unscrew the Door Lock mechanism: There are 3 Torx bolts on the side of the door. You can remove them.
3. (This is the fun part) Remove the door lock assembly: Drill out the rivots holding the assembly together. I told you this was going to be fun. (See picture. Rivots marked in red.)
Once the rivots are removed, you can pull out the assembly (see picture) and fix what's wrong.
In my case, the lock wasn't locking, and it was because the lock part of it was siezed with rust. I gave it some WD40 to loosen it, and then slopped on some heavy grease.
4. (Maybe even more fun..) Reinstalling the door lock assembly: Installation is the reverse of removal, with one exception. Note the yellow-tipped lever. This is going to be the bane of your existance for the next 3 hours. Now, take a flashlight and look into the hole in the door. Note the ridiculously undersized mount that it goes into. (It's attached to the interior of the outside door handle.) It's a small, rectangular hole into which that yellow-tipped lever has to go into. This takes a lot of patience and a little luck, as well as hand-eye coordination and imagination (You can't always see where it is.) Once you have it in place, and the outside handle catches when you open it instead of flailing freely, then you're done. Screw in the 3 Torx bolts that you removed in step 2 for support, then re-rivot the 4 rivots you removed in step 3.
5. Testing and Decorations: Test to make sure the door closes properly. If it doesn't, check the torx bolts for proper mounting and tightness. Sit the door panel on to the door frame, and push the velcro-like connectors together, as well as screw in the handle to hold it in place. Also, good luck with those snaps that were unsnapped when the door came off. Reinstall the interior door handle stuff with the 2 screws, ensuring that the door lock rod is securely snapped into the door lock button/handle.