You seem new to cars, in general, so I'll help you out; nobody else probably will on this forum anymore.

They make polyurethane body kits which can take a lot more damage and stay in tact compared to a regular fiberglass one, but the cost is more. If I were you, I would work on suspension and wheels for a 240sx. I used to have one and by the time you save up for those two items you'll realize the other potential aspects of that little car and then can really have some fun with it without spending a whole lot. Depending on the year, you can get a lot of second hand stuff that looks factory and looks great on the car.

Hope this helps, good luck.