I need to see if the 2nd cotract i signed at used car dealer is legal help!!!?

Ok I bought a car 7 month ago I traded my van (1,200.00) trade in and have paid 7 notes first thing is the car has gave me problems from day 1 I kept complaing to the dealer. They put it in the shop several times but it never helped..so finally its starts knocking real bad..timing jumped they say I will have to pay to have it fixed and they will add it to my payments. Cost 1,150.00 I go in to sign the papers to add on repair cost but what I didn't know as the dealer is being all friendly talking I bought my van that I traded for this car from them so I thought I could trust them as I never had any problems before..is that ts a new contract he was having me sign ...the contract does not have any of the amounts I have already paid ( down payment nor the 4,ooo I've paid in notes also the price of the car is higher than the sell price on the first contract and all the fees like taxes ect. Is being charged again after all is said and done this 6,ooo car will cost about 14,ooo is this legal? And what can I do about this matter