oops got to rebuild my rear axle.....

Well, I ran the '90 trooper without checking the rear axle oil and it started making all kinds on nasty grinding, squeeling, bad bad noises.
Time for a rebuild......are there any options out there/ possi rear and such?
also, How hard is it to install auto locking front hubs in place of the manual ones.......?

hit up www.car-parts.com and pick up a used one for cheap