Konads is a mate of mine, he gave me a hand doing the welding on my disco, which paled into insignificance compared to what he did to his! But hes right, we both did a welding course at night classes in a local college, cost about 140 quid or something, and now he has a decent mig welder. If it really is as bad as you say its sounds like it could be a couple of weeks work, the welding itself doesnt take long, its the prep and cutting out the old crap then making a decent patch! Get yourself on a course and get to it.
Learn by doing!!