If you don't have TIG welding experience I would recommend going with a resistance welder for sure. You don't really need any welding experience to run one of these. To do mold repair you not only would need TIG welding experience but you had better be pretty good or you are apt to cause more damage than do any actual repairs. The best one I am familiar with is Kwikweld X2, It can do about any mold repair you run into. You would not be able to repair cracked water jackets or other structural type welds, but then most TIG welders won't hold up to this either. There are a couple other machines available domestic and imported but they don't have as much range and I think they may actually cost more. You should be able to find them on the net pretty easy.