Well chances are you won't need parts in 5 years (I mean, I've never used this welder, but you know what I mean).
However, most welders all use the same parts. My Solar uses lincoln gun parts.. I assume this does as well (Tweeco? That what I'm thinking of).. Everything INSIDE the welder can be bought from any electronics place.. I wouldn't be too cnocerned with parts, except maybe the whole circuit board, but in that case, Lincoln and miller would charge you an arm and a leg for their boards anyways.