I am in the same boat. My 95 E300D (307K) tranny is on its way out. I was told my the local Mercedes dealer that when a tranny does not reverse.. it is the first sign of it going south. My car engages in reverse albeit after 5-10 seconds. Then I accelerate VERY VERY slowly and it seems to work so far. It drives great in forward gears.

The cost for the tranny rebuild is any where from $1500 to $2500 at indy shops and $4400 at the Mercedes dealer. I am going to push this tranny until I can no longer reverse and then get it fixed. Sorry I can't be of more help.

smk_texas
03 ML500
98 S420
95 E300D