Type 44 rear differential seal

[BBBurban at aol.com]

I need to replace the rear seal on the torsen of my 1990 90 Quattro 20 valve. 
 Any suggestions as to what I will need (P/N of seal if anyone knows it) and 
what else I should replace while I am there?  Any maintenance items (I do 
plan on doing the center u joint lube while I am there) that I should look at 
as well?  Thanks all. 

Hank 90q20v