Just for kicks here is a time-lapse video of me changing the evaporator in my R129 - pretty similar job. I followed the procedures in the MB-Star service manual DVD. Like others have said, its a labor intensive job but isn't hard. You will need some A/C skills and equipment when it comes time to pull a vacuum on your system and recharge it.

http://www.youtube.com/watch?v=A90TwLDsguU