I recently changed my 98 E320 with 80Kmiles trans fluid & filter. The fluid was filthy and there was a thin layer of sludge on the bottom of the transmission pan.
In my opinion it would be cheap insurance to change the trans fluid & filter. Make sure you use the MB approved synthetic trans fluid.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles