Hy 1herrick1, Firstly welcome, now to your questions the pits/holes in your wheel cylinder bores will accelerate the wear on your new wheel cylinder cups, if the cups must travel over them, if there in the center it's not a problem, cylinders can be rebuilt by boring oversize and sleeving with stainless steel, rather than buying new ones, so what price safety. You can drain the diff. oil by removing a few bolts from the bottom of the cover on the back side of the diff. Many suppliers have manuals for sale, rather than try and detail the rear wheel bearing adjustment here I would say purchase a manual and follow the procedure detailed in it, try American Classic Truck parts for the manual [they sponsor this sight], hope that helps.
