HELP! Canon Rebel XT's auto-focus stopped working mysteriously and I go on vacation tomorrow!?

out of the blue, my lovely Canon decided to stop auto-focusing, meaning I can't take pictures in any pre-set modes. if I had a little more knowledge of Manual settings, this would be okay but I don't really have time to learn that much between today and tomorrow. I'm using the standard 18-55 lens and haven't had problems like this before. I've also cleaned the sensor mirror and since it's Sunday I can't call Canon Support. help, please???