Bruce,
Drain it out pull the side cover.
Clean out the bottom of the case,reseal the side cover,that solves the leak.
this trans holds 6 pints 90 wt gear oil according to F S M (fact shop manual)
Big Hint...Rather than laying under the truck and trying to squeeze 6 pts 90 wt into this beast,
Pop the shift handle out the top,in neutral of course, and POUR the gear oil in the shift tower like a Gentleman
regards
steve sr.
