That's not law

UCC does not use the term of parol evidence. It, however, still says that if an agreement is final and complete, no prior oral/written agreement or contempraneous oral agreement can be admitted to contradict the agreed terms.

Any sales oof goods with a price above $500 needs written agreement, according to UCC statute of frauds.

This is not to say, that you can not raise raise issue such that you were induced or defrauded into the contract. As I said before, the sales rep merely said an opinion that you might be able to get a deal after Thanksgiving. It is hard to prove what they did wrong. Even you were defrauded, your subsequent exercise dominion by driving the car would have been recognized by court as ratification. The defendant can say, yes we defraud you. So? You know you were defrauded but your conduct ratified the contract so that it is still enforceable.

Take the car and try to find a loan somewhere else, such as home equity. Next time be sure request a writing, for goods above $500, intangible property such as stocks/bonds with value over $5000, any sale of land, including lease, and surety type agreement (somebody answers your debt).