Hey bud, I feel your pain! I'm 19 years old right now, and am a sophomore in college pursuing a double major in Biology & Biotechnology, which will hopefully get me into Veterinarian School. However, in my life that prior sentence is mundane compared to the amount of interest and effort I have and put forth into my car. It's almost sad. In fact, the man that I race with was needing some help, so I stopped by on friday, and he laughed saying that "there's 1500 hot girls up at the football game and you'd rather help an old man work on his drag car--you're definitely addicted!" I'm not dumb enough to neglect my school work for my hobby/habit, but the crossroad I run into is this: I can save what money I make from my jobs and put it toward school, or take out MORE student loans and end up paying them back for years upon end with interest and build on a car that I know isn't going anywhere. I ended up coming to a compromise and spend enough to have fun, knowing that in later years I'll have money. I also had to realize that I don't know one other 19 year old kid that has his OWN (as in fully funded by himself) 8 second pro-mod car and still has the money to send himself through college.
It's great to hear that you're going to college, and I think that the financial situation is where most kids our age arrive at a conflict. That's where schmoozin with other racers/rodders is great. I've learned 10 times as much from them than I have from my own experience, even if a little is BS. If you can find one that is generous enough to even let you watch when he does some of his work and tuning it's almost as fun as actually doing it.
Whatever you decide, remember there's always the future and a well paying, car-building-funding job ahead of you.