When I did my first oil change, the oil place that last did it torqued it down too far. I couldn't get it off and ended up stripping the bolt. I was finally able to get it off with vice grips. Vice grips will indefintely get that sucker off, but do remember, it's all about leverage.
You can get a replacement bolt from anywhere. If you have another mode of transportation, get the bolt off, take it to a auto store/dealer/even an oil change place. (Once they see the bolt, they'll match up the neccessary thread pattern in no-time). I got mine through an oil change place. They charged me like $3.99, about the same price at any auto store.
Good luck!