I think it depends a lot on your willingness to learn and your motivation. You sound young, so what would you rather spend your time on? Working, cleaning and tinkering with your R/C car, or playing video games? If gaming or your friends hold your interest you might not have the "time" to fix your car when it breaks or to do the maintenance.
During the summer when I am real active I easily put a hour or two a night into wrenching on my stuff. But my cars are always tight, detailed and ready to race.
I have been doing this since I was 8 years old. When I was that young did I know how to work on my cars? No. But I was motivated enough to figure it out and while I made a lot of mistakes, I also learned a lot. When I was a kid, from say 10-14 all I did was hang out in my room wrenching on my stuff. Playing with, breaking, then fixing my cars. It is expensive.
Nobody can start out knowing how to do stuff, you've gotta learn. You learn by asking us make believe people on forums, and the real people in hobby shops, and read some magazines (start buying XRC) read every article you can on rc411.com.
Your dad will have to help you, he will have to teach you how to use tools if he himself even knows, and if he's not willing to do so he should get kicked in the nuts...thats my opinion anyway.
I would not start out with a nitro if I were you. I'd suggest buying something like a Traxxas Rustler or Stampede, electric. They are fun, they are less expensive, and some of the parent worry factors are missing like the noise (you can't bug the neighbors as easily) and your less likely to burn the house down without nitro fuel. Plus if you can't figure out the engine yet you don't need to pay the hobby shop to fix or tune it.