I almost took the automotive route career wise. I actually really struggled getting into college because i was so convinced it was right for me that i denyed all my acceptances to school. In retrospect, i'm very happy i didn't go that route. One of my best friends actually makes about 200k a year work on large diessl engines. He enjoys it but his work schedual is crazy. 18 hour shifts sometimes, work starts at 5 am many times. Out side of that, almost every mechanic i know pretty much hates their job. It's just not the same thing doing maintainence stuff on regular cars, day after day.
I do know two people who abolutely love their jobs. Both opened up their own businesses. One is my father's friend, he has a shop that specializes in british cars, his passion. The other, has a small import shop, basically out of his house, again, his passion. There are huge risks invovled with this though and alot of money can go down the drain. If this is your goal, start now with a small online store or something similar and see if it fits you.
I'm speaking totally interm of being involved with the mechanics side. Obviously there are far more jobs out there. If you get a mechanical engineering degree, you can go into many things. But don't plan on it being an easy road. This is probably the least realistic way to go. But you may find you enjoy things similar to cars that are easier to get into. To be quite honest, and fairly blut, if you only want to work with cars you probably arn't cut out for it as an engineer. If other mechanical things don't spark something, you won't enjoy that field of work.