I am sorry to learn of this situation. If you can show that the dealership actively concealed the damage to the vehicle (either by obscuring the damage, or by hiding the pertinent records from you, or by manipulating data that they provided to you), then you can claim that they committed "fraud in the inducement" and the contract becomes "voidable" (meaning that as the injured party you can void or enforce the contract at your option).
However, if the damage was visible to the unaided eye (it could have been identified by a buyer at the dealership, and the dealer made no affirmative misrepresentations regarding the condition of the vehicle, this makes it very difficult to challenge the transaction (the problem is that they didn't misrepresent or defraud you, but rather the claim is that they should have disclosed something that was visible on the vehicle).
You can try mediation in these cases - use a third party neutral to try to help mitigate your damages here (get the dealership to cover at least some of the cost of repair), or use the BBB to do so (the BBB is free to you as a consumer, but they are not always as helpful or quick to respond as a local mediator). If you decide to try a mediator, contact your local bar association and ask for referrals - you can use either an attorney, a retired judge, or a professional (non-lawyer) mediator for this type of consumer transaction.
If you believe the dealership is engaged in fraudulent business practices you can also report them to the Illinois Attorney General's Office - they can investigate the matter and take administrative or criminal action against a business, but they will not unwind your transaction or get your money back (you must either negotiate a resolution or sue the dealership for fraud and breach of contract).