Rear u-joints are super easy to replace! You'll want to replace both joints at the same time, chances are, if one failed, the other is on its way. You'll drop the driveshaft by the four bolts on each of the flanges (remember to mark your driveline). Pop out the four clips on the u-joint and get to knocking those babies out! By "knocking those babies out" I mean hammering one side out enough to remove the cap, then going in reverse to pull the other cap off... Installation is the reverse of this process.