I have done this just this year in my 104... I believe although it is a Hydro, it is the same rear end in the Diff housing.... I took a pair of needle nose pliers and removed the C-snap ring on the end of the axle shaft and it slides right out, the clip comes out very easy... The oil seal you need is 721-0187. Not sure the size, but thats the item #.
Check out Pages 2-28 and 2-29 in this manual....
http://ccmanuals.info/pdf/1x4-5%20Service%20Manual.pdf