Anybody know the specs for the oil seal on the front of the Sidekick t-case where the front drive shaft enters. I've got a leaking seal that needs replacing but I need a replacement ready before I pull the old one.

I would bet you a dollar that its the prop and not the seal. 

If you have a good spare prop try it first,   When you get the seal your replace it and with mine it still leaked , I question myself thinking i must have pinched it,  i had a new ta case on the way so thought cool no more leaks ,   and it leaked put a new prop in and wayhey no leak

I've changed both front and rear output seals before with positive results.  I don't think there could be any other problems than that.