A friend of mine has done just what you're talking about. He used a hand-held grinder with fiberglass cutting disks to cut the doors/lids of the grill out. This makes a much nicer and much smaller cut than a torch. One thing he did was to cut all of the door out except the areas right next to where the hinges go, and a couple small spots on the opposite side. This allowed him to weld the hinges on while everything was in perfect alignment. He then cut through the remaining uncut areas and the door/lid functioned perfectly.