I'm with Ben. I bought my GTR when I was 19. If I didn't I would have a second house already.
However, everyone is young once and wants to have fun.
I suggest giving the car a full service, replace all worn suspension bushings and replace factory shocks and springs, new brake pads and fluid + braided lines if you want and then get stuck into the power mods.
Stick a front mount on it and get a boost controller to start with.