I've done a bit of ally welding in my time and if the hub has been welded I wouldn't worry too much about replacing it unless it's ugly as sin. As for the grub screw, I reckon you'd be better off spending the money on a set of allen keys rather than paying someone to undo it. You would also have put another tool in your shed. Have you tried a neighbour or a mate? Surely someone can loan you one.
