if you are handy it is possible to do yourself. prices vary depending on ABS and such. I can't say "how Bad" the specific problem is, but when one of mine went totally out on the highway it was vibrating so badly the wheel was beating on the suspension. They should show signs of being bad long before that happens though, I just thought the symptoms were of something else.
there easy to do as long as you have the tools to do it. i believe there (3) 14mm bolts on the back side for the hub assy, and a 20-23mm nut in the center for your CV shaft. your just going to play hell getting it out of your spindle bracket because its kinda a "press fit"
as said above. they range in price.
4x4 truck 2wheel (rear) ABS is just over 100 bucks. (i think)
They are usually sold as one unit with the hub (wheel studs and all).
and like "Wah" said they can be a pain to get out. There are 3 bolts that hold it in, so the flange is triangle shaped. Once the bolts are out I just hosed it down with penetrant and beat each side of one of the flange corners with a hammer until it begins to rotate in the spindle/knuckle. I managed to replace both sides with this method.