Yes, he will still be able to use the truck. Probably have to cut the bedliner to fit the fifth wheel hitch to the bed of the truck. Then he can caulk around the opening with some rtv rubber cauking, if he so desires, to keep the dirt and water out from under the bed liner. Or he can remove the bed liner and sell it. But it will protect the bed if left in and just cut out the opening. A zip saw should do the trick. Just raise the bed liner up enough to get the saw blade away from the metal and cut it out.