Changing the pumpkin is just remove and replace. You'd need new Ujoint caps and bolts for the driveshaft and half shafts.
Let's see..take off the skid plate, drop the driveshaft, unbolt the half shafts at the pumpkin and slide/compress them out of the way, unbolt the long stabilizer bar running from the pumpkin forward, unbolt the pumpkin..Gen 2 cars would need to remove some of the rear exhaust I guess. There might be 1 or 2 more little things I didn't think of, but there's not a lot to getting it out overall.
Typically around $125 locally to have new gears put in if you drop off the pumpkin at the shop. Not including the ring and pinion you're putting in..