I think your talking about the driveshaft center support bearing on a 2-piece driveshaft, and not the differential side bearings which are sometimes also called carrier bearings. The driveshaft has to be removed and the 2 bolts holding up the center support. After the shafts are out the bearing will need to be pulled off with a special tool puller that goes under the bearing and pushes against the front of the rear driveshaft. When the old bearing is removed then install the new bearing. It will need to be pressed on, again using a special tool to seat it. Most shops could pull and oress the new bearing on for you.