Hinges can be welded, have seen a couple repaired this way but probably not worth it if you're not going to shoot it. I do still shoot mine occasionally, always handle it carefully when opening the action. Some people I have talked with think most cracked hinges are from people snapping the barrels over and that the design just wasn't robust enough for rough handling.
They are neat little guns and I enjoy shooting mine now and then. The Navy Arms ammo is getting hard to find, last batch was imported @ 1999/2000 as far as I can tell. I have also shot some older stuff that I have found, usually loose rounds from partial boxes. Have considered getting some of the reloadable cases that use a 22 blank as a primer just to try them and see how they work.