Walter,
Recently I've had the misfortune to have to have the AC evap replaced in my 92 300SE and
did a lot of research before doing so. Included was using a leak stop product which slowed it down but kept returning worse until I had to bite the bullet. I've put a 5.0 into a 190 but would not even think of doing the evap after I saw pictures of a 300E with its dash apart, and the factory time is roughly 14 hours. On my S class it is 21.8 hours. If you feel good about it go ahead but a strong warning: as you get the dash apart and are ready to pull the heat/ac unit out there is a tube which runs from doorpost to doorpost. When you remove this crosstube, do NOT, DO NOT, open a door because if you do there is a good possibility you will crack the windshield. The tube is a designed structual member of the chassis and an open door will stress the windshield frame and because the glass is glued in, it will crack. The local dealer here cracked a few before learning!! Just a
fair warning which is probably not in books!

Good luck with the evap.

TobiasMB
300SE, 300CE, 190/5.0