I had to get a machine welded, the guy that did it was incredibly knowledgable. there are a lot of people who do welding on cast, but from speaking to the guy that did mine it looks like not many do it correctly. I would say that if the part involved will be supporting something that for instance spins at high speed and could cause potential injury if it fails, then I would want somebody who is an expert in these things. if it is say a leg on a machine and less dangerous then maybe learn what you can and have a go. unfortunately specialised welding can be extremely expensive, and cost more than rebuying a machine. sorry to sound like a killjoy, but it's safety based.
looking forward to seeing this exciting item
nathan