I can't imagine using a stick welder to plug weld sheetmetal. I mean, I have only used one years ago on a frame but a stick welder and a Mig are MILES apart.
Beg barrow or steal a MIG. There are places that rent them around here. You can buy a nice set up for about $600.00.
If you want to read a "Basics of Basics" to MIG welding (including a explanation of the "plug weld") go to
http://www.camaros.net/forums/showthread.php?t=13135 print it out and read it over and over.
Brian