Don't bother.
I tested this at Activision a couple years ago and spent a full month driving around and smashing into things...get this...for money. That's right. You take the car you are supposed to "pimp" and smash into anything and everything you can with it for money. You can also do short minigames, like the god-awful rhythm-based "ride the whip" game in which you press buttons in time with the atrocious music. When you finish, you are rewarded with money to buy parts for pimping your car.
The only enjoyment in the game is in the silly cut-scenes where Xzibit meets his fans and mentions how he will "pimp their rides". There are some funny moments here, such as when a D&D geek gets his ride pimped.
Overall, buy this as an April fool's joke, if you buy it at all, but I do not recommend it.