I think you are on a roll. If it were me I would not only drain the trans of ATF but also the torque converter. I would then drop the trans pan and get a genuine MBZ trans filter and gasket. Install them.
Pour in some TransX or something like that along with the rest of the ATF. See whats left!
Some people would not doubt disagree with me, but I often find some Benzes are actually ok, just need some TLC.
It will cost you a lot less than the $100 or the $600. If this works then go to the trans flush.
Keep us posted!
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)