Just a small point, but one alluded to earlier in this thread. When I was MIG welding a long time ago, I used both argon and CO2 and I found that the argon worked a lot better. It's more expensive, but gives smoother welds with less splatter. Welding sheet metal is tough enough at the best of times, so I concur with the advice to practice, practice, practice first! When you're confident you can do it well, then go for the real thing.
Let us know how it works out!
