The hub actually doesn't wear so no real need to replace them. To replace the bearings, you need to remove the steering knuckle and press out the old bearing and hub. Then press the hub into a new bearing and press all this back into the knuckle. A NAPA with a machine shop will do this for about $80 parts and labor per knuckle. Getting the steering knuckle off (and back on) the car is a fair amount of work but a Haynes manual or service CD will be a big help. You can loan the special tools from AZ for free. (Axle socket, hub puller) This will take about 3-4 hours per side. $200-$250/side would be a fair price for a garage to do the work.
The only reason you would need to replace the hub is if you beat the crap out of it getting it out of the bearing. A decent machine shop with the right equipment will have no problem handling pressing the hub in/out with no damage.
