I do not remember the fluid recommenended, but the converter has a drain plug as viewed thru the "cage" forward of the pan. I used two mirrors to view while advancing the engine from out front.
Me, thinks it is a 5-6 mm allen plug. Fill, run, & refill as required to insure TC is filled.
BTW, the fluid used is nowhere as expensive as the dealer tranny fluid for the '99 E300D.

__________________
Gary
Experience is something you get, Just after you needed it....
'99 E300 295K, '83 300D 220K, '75 240D 185K sold
'80 MCI Bus Conv DD 6V92TA, w/4 cyl. Kubota diesel GenSet 12.5KW