you need to clarify between a fender, a 1/4 panel, and a bumper first. A fender and a 1/4 panel are one in the same. As Erc stated the 916 BUMPERS are additional pieces. If your bodyman is going to attatch the flares, mold into the body, FIT the 916 bumpers and smooth out and paint the whole car then 5K is a crack fix price. Go for it, but dont expect a show car.
NOW, if all he is doing is glassing the flares on and blending, bolting the bumers on as they arrive, and scuffing and shoooting the whole car, that is more in line with a 5K price. Again, don't expect a show piece for that money.
Also make certain he is going to use the proper bonding materials to attatch the fiberglass to metal, otherwise, you'll be seeing it in a few years.