Think of where you want to be in 20-30 years as well, probably not at a dealer, where would you move up to? service writer? Manager? Maybe not without some school. What if you get laid off, can you find another job like it?
In my brief time looking for engineering jobs, people with real world experience in anything are pretty damn well off finding a 50-60k a year job straight out of school, maybe with a year of internships prior to graduating.