I had a rear pinion seal replaced on my 91 Chev truck for like $35. a while back. Might be a alternative to doing it yourself to have it done if you can get a good price from a reputable mechanic with the right tools and the experience to not mess it up.
I have found that you can get the pinion nut off with a 3/4 inch socket and pressure bar and a small sledge hammer by giving it a good rap. Good luck~~Huck
