Turbodiesel,
I too have a '99 E300 which I purchased new. I just had the 100k service done by my trusted independent shop. He recommended a trans fluid and filter change. He does not believe in "lifetime" fluids. The problem with "lifetime", especially for diesel owners, is that MBUSA's idea of lifetime and ours usually differs in definition. My mechanic said the trans fluid didn't look too bad but that it needed to be changed. I'll get it changed again @ 200k.
Enjoy,
Ken