I do welding and fabricating for a living, it wouldn't cost to much but it all depends on frame material and how big the cracks or splits are. Usually when it comes to cracks in the welding the old welding gets cleaned up (or removed) along with metal around the crack so that it makes for a clean welding area for good penetration of the new weld. As i said not expensive just time consuming for the welder, tryabean is right find your local metal fabricators and pop down with the frame and ask them, whats the worst they can say... sorry cant help you?