Any of the above interventions require the tranny to be out of the car. BTW, where do you see the oil coming from? If it's the bottom of the bell housing, all of the previous recommendations will apply. If not, you may just need to replace pan gasket, dipstick o-ring, output flange seal, none of which require removal of the tranny.
Good luck. Drive train stuff can be a bummer..

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Jeff L
1987 300e
1989 300e