I am considering purchasing a single-owner 76 Cadillac Seville with almost 50,800 original miles. While test driving it, I hearding some noise in the rear. The mechanic selling it put it on the lift and said it needs rear wheel bearings. Is that a major job? What parts are needed? He said he would send it out for repair, because he is too busy right now and he might be spending around $500. Does that sound realistic?