You don't mention what year Mustang. I will assume that it was new enough to be a bearing and hub unit.Are the front wheel bearings difficult to change? I'm no Mr. Goodwrench but am able to do some things. I changed the bearings on a ford mustang a few years back.
While I have not had them apart yet, looking at the pictures of them they also have the antilock brake sensor in the hub assembly. I have had these corrode on other Chevy trucks and they can make the brakes act funny on slow speeds. The bearings are sealed and not like old bearings that you can repack as a maintenance item. They will go out from age and wear.My question is why? Never heard anyone changing them on this Forum???