Follow up: Replaced my rear door latch this weekend. Took me exactly an hour. Everything was reasonably easy to figure out. I did waste a little time by removing the license plate lights (2 screws each) and the license plate while I was looking for the hiddeen screws that held the lock actuator to the inside of the door. You don't need to remove those. The screw heads are covered by the trim plate that goes all the way across above the indentation for the license plate. To get that trim off, remove two screws on the outdise and two 8 mm nuts oon the inside.

I bought my part from Phil at Fastlane. His price was $90 v. my local dealer's price of $130. I won't buy parts again from Dick Dyer Mercedes in Columbia, SC. What a scam operation. Phil was great to work with. I ordered online, he called shortly after to confirm some details, and I had my parts when promised. Thank you, Phil.