Depending on the shop, you're looking at about 2.5 hrs. labor, so at my shop that'd be $100 labor, plus parts. As far as the rear goes, the only thing in your favor is the driveshaft will be out, not much help. It would however, be a good time to change the tranny filter, and check out the ole' converter too. Also replacing the FRONT seal in the tranny is a good idea at this point too. It has the same mileage on it that the leaking rear main does.
