rear main seal leaky - little advice?

[<ghare@bellsouth.net>]

1969 2000 - Since rodents ate my manuals - is it possible to do replacement on 
the rear main oil seal without pulling the engine/tranny?? One of the guys here 
at work thought it could be done up through the oil pan, but I don't 
necessarily trust him.

ALso - any idea what a fair price would be for a U20 engine, running good, 
unknown mileage? My brother says one of the people on his mail route has one, I 
don't know what to offer if it's really what he says it is.