How difficult is it and how do you replace broken lug bolts on rear disc brakes? It's a 2003 4wd Blazer LS.

 

The worst part will be removing the rear drum. It can get hung up on the parking brake shoes. From there, you just drive out the old lug, then install the new one. You'll want to have a few heavy washers and a spare/junk lug nut to pull the replacement stud in.