Meekajahama

Sorry if this has been answered but I've searched and have not found success. I have a 1998 3.8L Camaro only upgrade is a flowmaster exhaust. When I accelerate the car makes a loud whistling or howling noise from the rear. It only occurs when I step on the gas in drive as it does not occur in neutral. I found through searching it could potentially be carrier bearings? If you have any suggestions it would be greatly appreciated. Few more quick questions:
1)How much does a new rear end cost?
2)What exactly makes up a rear end?
3)How much do carrier bearings cost?

If you have any other suggestions could you also offer an idea of how much it would cost. I'm not very experienced so this would have to be done by a shop.
Thanks for any help you could give.