That blows. The pinion bearing usually seizes to the pinion gear. When this happens, it locks the pinion gear into the case. Probably have to torch it out...total PITA. You'll have to torch it from the yoke side. You'll need a sledge and a big, sturdy, punch (like an old 3/8" socket extension).
The idea is to cut (melt) the bearing and race off the pinion gear. Use the punch to knock the pieces out. Normally I wail like hell on the end of the pinion gear to drive it out...but that is with no intent of saving it. I've never tried to salvage the R&P, but you might be able to. Use a brass sledge to save the threads on the end of the pinion gear. You should unlock everything and drive to a shop with a lift and a oxy/act. rig...hard to swing a hammer lying under the truck. You will have to SWING it with everything you got! Make sure you got a catcher standing by so the pinion doesn't fly across the shop.
Once you get it out...check the pinion gear for damage AND also check to see if the old race spun on the gear. If so...you should replace the R&P, as a new one will not properly fit the scarred shaft. Good luck.