JRods Firebird

Well my bird has been sitting for little over 3 months and had it covered. With a so called car cover that works wonders, well the cover rubbed through out the whole clear coat. Finished the interior and decided to put some gas in it and drive it. At 1st it felt like its been sitting for 3 months but a loud whining noise is coming from the rear. I replaced the diff fluid just before winter hit but still heard some noise. Now its much louder. Car warmed up and drove much better but the noise is getting to be a pain. Will wheels bearings cause this type of whine. I said will maybe the brakes but the noise doesnt change when depressing the brakes. If so Ive never did a type of job like that. I dont really have a repair shop in mind but what would be a fair price for a job of replacing the wheels bearings on the rear of a 91 Firebird. Anyinfo would help.