What's keeping you from doing an oil change? I think that would be a good place to start. If you aren't willing to do your own oil change on your own car you probably aren't going to be happy doing it 10 hours a day on other people's cars. Same thing goes for tuning, get a tactrix cable and start datalogging and learning what you are looking at. There's plenty of information out there about how to do it, you just have to take the initiative.