Hey guys. Haven't' been on the road since August and hope to get it running soon. 69 Camaro with a 350 and a TH350 trans.

Leaking from the transmission rear seal where the driveshaft enters the transmission. Should any fluid be in the tail housing? If not, other than replacing the tail housing to main body seal in the transmission, is there anything else I should check?

Also, how do you fill the trans with fluid without the fluid running out.? I know the air has to escape when filling it up, but is there some garage guy trick to keep it from running out when you're filling it up?
Thanks much