wheel bearing noise - is it really there?

I took my car (85 190E 2.3, 116K) for an oil change, and the guy said I need to replace the front right bearing, as its making a "lot of noise" - I have never heard that noise, I tried to notice it with the windows down, driving slow, etc, etc. but nothing. How can I find out for myself if the bearing is indeed bad, or the guy just wants me to part with some $$$? Also, he said that he would repack the left front bearings - is the labor involved in repacking the same as in replacing the bearing, because in that case I might as well get it replaced? To my knowledge (I have had the car since 80K), the bearings have not been replaced. Also, how bad does the noise get before it actually breaks down - I mean, what kind of a notice would the benz give me before collapsing?

thanks for all your help folks!

Rags