welder flux to mig???

Look at the back of the welder, it should have a brass nut for the 75%/25% CO2/Argon mix of gas you'll need. You'll need to buy a flow regulator kit (conversion kit as you call it) as well. That will hook up the tank to the welder. For doing body work you'll also want thinner wire, such as an .025 or even .023 I think is the thinnest.

Look for your local Praxair Dealer, they sell the Gas and also Rent the bottles. Buying a Bottle can be expensive, if your on a tight budget. I rent my tank for $10 a month from them.

Hope this helps

Eric