If your torqe converter seal was leaking the transmission have to remove & replace seals,gaskets. to refill ATF is from your trans filler tube,to change filter you have remove trans pan replace pan gasket & filter,there is two drain plugs,oil pan & torqe converter remove plugs drain fluid then replace gasket,filter,you must replace drain plug seals.
hope this help.

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MB STARS Master Guild Technician,12 years MB tech
6 years independent shop owner