Your best bet is to take out a 1 or 3 year subscription for your car from www.alldatadiy.com
. The entire procedure is in their GM service manual section.
The bearings are housed in a capsule - you cannot replace an individual bearing - you replace the entire capsule which is bearings, mounting flange, wheel studs, speed sensor - all one piece. To see what you're replacing, take a look at www.rockauto.com
, surf to your car, brake/rear wheel hub, rear wheel bearing assembly. Click on the little picture or the (!) icon for a larger view. Replace both right and left rear capsules at the same time. Use ACDelco/DELPHI. Not a cheap job. Parts are $500 alone, not including brake pads and/or rotor if you need those, too. (special procedure for rear brake pads - caliper reset) Make very sure the brake rotor mounting surface is clean and free of rust when you put it all back together.