No you will be alright, the head is generally heated all the way through before any welding comences, this ensure good flow when welding. As long as the correct wire is used you will be fine. It might be that the hole area may need to be milled out to get a got gob of weld in there then just machine it back to the original face then drill the hole in the correct place. My cousin has got his own business doing this kind of stuff, if you get stuck drop me a PM and i will have a word with him and get a price. The only shitter would be the postage.