I put those numbers in my spreadsheet, and I get the same $259/month in savings @$3.00/gallon and 350 miles/week. It would take you 33 weeks to break even, and not the 1.7 weeks that yours outputs.
Debt as of 1/1/05: $34,354.48
Debt as of July 4, 2007: $0.00 explanation
I'M DEBT FREE!!
I'm now a reasonably successful gunblogger.