I build and repair bicycle frames and, as far as frame repairs go, this one is pretty easy. Welding that dropout back together is not going to affect any other joint around it and the weld will be in an area that doesn't require it to be ground flat. You probably don't want to take it to the neighborhood guy with a welder, though. Someone with TIG welding experience would be the best option. Whether it's worth repairing depends on if you can find someone near you to weld it for a reasonable price. If you were near me, I would do it pretty cheap or free just to keep it on the road.