PLEASE HELP!!!!! Read please!!!!!!!!!!!!!!!!!!!!!!!!…

Today I went to look at a 2010 buick lacrosse. I gave a trade in that they offered 5,100 and im also putting 5,000 down. My credit score is good. The one the car dealership used was 704 and the other two were even higher than that. So let me mention im 20 years old. Ok i need a opinion because I went to do the paper work today and plan to pick the car up friday. This is where i don't have a understanding. They gave me a interest rate of 12%. Can i find a better deal? Should I back out. Another thing I left out is when the dealer gave me the paperwork he brought me my credit score that read a 651. I keep up with my credit score membership so I checked it when i got home it it was just absolutely wrong im going to contact them tomorrow about that. What do you think about this situation?