Update. If there is a drain for the converter, I can't find it. Drained what I could from the pan, about 2.3 liters. Fluid looked to be in decent shape. A reddish brown, still relatively clear. Car is MY2000 with 36k. Brought level back up to full with MB fluid and the special MB dipstick. I guess a full flush can only be done at the dealer.

glenmore
1991 300CE
1990 LS400
2000 C280