How would a class action help you? You didn't actually tell us what the problem is, but if you think the contract is wrong then you can take it to a consumer lawyer in your area. If you just signed a bad contract because you didn't read and understand it before signing, or relied on something "behind the scene" not in the contract, it is generally your responsibility.
Car dealers are very good at manipulating numbers. And manipulating consumers. It is hard to understand what you are saying. It papers that you thought the dealer was reducing the price by $500 but none of the numbers changed on the contract. How did you not catch that before signing? The Georgia courts are unfriendly to the idea of contradicting something like the price that is spelled out clearly in a contract.