Well, I own a Lincoln Mig-Pac 135 (same as Weld-pac but with Mig kit installed at factory) and let me tell you, you won't like the results you get with flux core. You WILL burn through 22 gauge metal with it. If you can't afford the Mig unit then have somebody else do it for you. I'm sure you can find someone in the area who will do it for a case of good brew. That's usually my fee.
You will also need to practice at least two hours with scrap metal to get a decent looking weld. You will want to get an auto-darkening helmet, too. Flux core welding is only good for 16 and thicker gauge metal, and it spatters pretty bad.
To arrive at the proper settings, follow the recommendations given on the sticker on the inside of the hatch on the welder where the wire spool is mounted. It's a pretty good baseline. If you are burning through then go to the next step lower heat setting, and if you have problems with the arc extinguishing adjust the wire feed rate. Ideally you want the weld to penetrate through most of the metal and leave little to grind off. You should see some slight marking on the backside of the seam but no holes or heavy warping. You also want to do the welding in short sections, letting the metal cool before continuing. That will keep warpage down.
