Like bentley mentions, if your bearings are so far gone that the hubs are damaged, your front wheels are going to be wobbling bad and you would probably smell something burning up from the friction heat of the bad bearing. Noisy bearings are fairly common and you can drive on them a long time before they fail totally and damage a hub or axle. Ditch the guy trying to sell you hubs, he probably doesn't have the right tools to do the job without killing the hubs.
