i replaced mine on my 2001. Luckly i knew i guy who had put a flat bed on his pickup so he gave me his original bed. just so happened to be the same color and everything. so as far as cost, i can't really help you.
If your wondering about removal/install, it is a fairly easy task. 6 or 8 bolts if i remember right. Remove the rear bumper and disconnect the wires for the tail lights. Also have to disconnect the fuel filler neck, but thats about it. Make sure you have a couple people to help you lift it off. Not that heavy but awkward and too much for one guy. I used a tractor with a loader and just chained it up to lift it off, only because i did the project on my own. If i remember right, it only took a couple of hours or less.