Here are a couple of previous posts that should help.
MB Approved Trans fluid (list is about 2 years old, but you can always call MBUSA and ask for the "Factory Approved Service Products S-0473-00M"): Best ATF for MBs? Synethietics?
One poster's experience and thoughts from his mechanic are located here: Transmission filter life expectancy
S, J.R. Brown
2000 G500 LWB Obsedian Black
2005 Toyota Tacoma Access Cab Off Road Sport
1993 Volvo 240 Sedan Anthracite
1980 450SEL Champange (owned it for 15 years. Great car)
1986 280GE LWB Anthracite (Sold it and kinda wish I hadn't)