How do I replace rear end?

This is a loaded question . Do you want to replace the gears or seals or bearings a complete rebuild or just replace it with another complete axle you got from the wreckers. The axle is the easiest but will probably take the longest. Do you have access to a hoist or are you working off the ground . I'm going to assume your working off the ground and are replacing the axle complete and are not going to crack it open . in this case you undo your u bolts on the axle on each side remove the driveshaft and disconnect the brake lines and ebrake cable and remove the vent hose and shocks then swing it out by moving it from side to side to get it out from the leaf springs . You'll need some strong guys to lift it this is not a one man job. And installation of the replacement is reverse everything you did to get it out . As for what tools you need you'll need acess to a complete set and you may want a big red wrench handy cause the u bolts will be on there tight ,probably seized . When reinstalling you need to make sure the axle is seated properly before tightening it and you may want to do yourself a favor and not reuse the u bolts. Dont forget to bleed the brakes after you reinstall the lines Hope this helps