I need immediate help! Job interview dilemma!?

I have been applying for jobs for 2 years now, and have gotten NO responses. I have applied everywhere I could. I applied to the local school system(s) several times for computer tech, warehouse, anything. Just before Xmas, a local small home-service computer tech company hired me. (This after being several years out of the industry, too) I did a couple weeks training, and am now pretty much on my own. It is a commission-based idea, so the more services, parts, etc, I sell, the more I make. Also a minimal health plan, etc. Today I got a message from the school, wanting to interview me Monday AM., for a tech spot. Its a State job, (although on the news tonight it was all about cutbacks) What to do? Keep the bird in the hand? I have to work Monday! How do I swing the interview? Or do I write it off?