Depending on the why, I just asked one of our techs and he said that if the tolerances are off just slightly on that hub, you'll have trouble latter. If you really want to do it right, replace both the hub and bearing together. There may be a slight grove from the race of the bearing on the hub, if that is the case, the new bearing will not sit right and you will have trouble latter. I have seen this, before. The money you think you'll be saving on not buying the hub, will cost you in the long run. Unless you have a full blown shop, that bearing has to be pressed off and the pressed back on the hub.
I urge you to SERIOUSLY consider this advice and save yourself time and headache, just replace the hub and bearing together. Take it from someone who see's this day in and day out. I know others in here may disagree with me, and some may have done it without doing the hub and gotten lucky, but the percentages of those that didn't and had to do it again only to have to replace the bearing and hub again(once the bearing is pressed on, it can't be reused) far outweigh those that have gotten lucky.
If you go to any dealer or independent, they will more likely tell you to replace the hub and bearing as a unit and there is a reason for it. In fact, I'd be surprised if any place would do just the bearing and then guarntee the work.
As I have stated I offer discounts to TN members, but wherever you buy them from, and whether you purchase them from me or not, please, do replace them TOGETHER.
Thanks for the replies. I was under the impression that the Hub was a contained unit but sounds like I will be needing only to replace the bearings.