im 13, and im wondering if i should take up mechanics, and when i get older and know about cars, should i fix it, it been sitting there for a while ... will it be worth it ??

If mechanics is your passion then I would go for it. It's not easy to find a good, solid car that you can work on. I would also suggest asking your dad for help with it. It will be a good bonding time for you and him. And even if there's not that much wrong with the car, every little bit you can do will help.