Belt Replacement

When I checked my serpentine belt (or at least I assume its the serpentine belt) on the front of my 4.6L it's extremely worn and the ribbing is starting to crack. I know it needs replacing, but is it something I could do myself? If not, how much should I expect to pay elsewhere for it? I checked with a Ford Dealership and they wanted 90 dollars to do it and 48 dollars just for the belt.. :-/

A serp belt change is easy. Your car should have a diagram under the hood on the radiator support or on the underside of the hood showing how to route the belt. There should be a spring tensioner that keeps tension on the belt. I havent been under the hood of a newer mustang in a while so I cant remember for sure, but the tensioner should have a square hole in it. Just take a 3/8" drive ratchet put the drive part in the square hole. It may be 1/2" I cant remember for sure. But just rotate the tensioner away from the belt and slide the belt off of a pulley. Then route the new belt around the pullies like the old one was and your done.