I'm not much help on the specifics, but I do recall getting that pinion nut off was a real ordeal. Finally had to use a 3/4" drive deep socket and a cheater bar set on a floor jack. When I got it off, I realized the last person had used some kind of thread locker on it. If you have a hard time getting it off, you might try heating it up with a propane torch to soften any thread locker. I do remember I got my seal at O'Reilly's auto parts, but they had to order it.
