My question involves a consumer law issue in the State of: IL

I recently purchased a used car in the state of IL. Upon driving away from the dealership (within 5 miles) the car stalled. The dealership told me they'd allow me to trade the broken down car purchased just minutes prior for a different auto. A new sales contract was drafted and signed by both parties. So I left with two contracts, one for the deal on the first car and one for the deal on the second car.

Fast forward 20 days, I get to the DMV to pay for license plates and the contract submitted to the DMV by the dealership was my signed 2nd contract with all the sales figures marked out and replaced with hand written figures from the 1st contract. By doing this the dealership is showing a lower sales tax collected, a higher purchase price, and a lower trade-in allowance. Meaning I have to pay additional sales tax. My contracts show they collected a total of $1142.00 in sales tax but they're only reporting collection $949.00. When I called the finance manager at the dealership, I was told they did away with my first contract and combined the two into one new contract, using my already signed contract and superimposing the new figures. When I asked him about the sales tax difference he said just let me know how much it is and I'll send you a check but asked me not to raise the issue with the DMV.

After having a local dealership look over the two original contracts and the new hybrid contract submitted by the dealership they noticed that the dealership kept just over $5000.00 extra from one contract to the next. On top of that they agreed in the original contract to pay of my outstanding loan in the amount of $13,200.00 but the dealership sent a check for only $10,900.00 to my loan holder. The finance manager said he'd send me a check for the $2300.00 difference but it's been "in the mail" for over two weeks now.

Here's my dilemma, my temporary license plate is about to expire and I don't know if going to the DMV and paying the additional sales tax to get a new plate somehow says I'm agreeing to the paperwork and in my option fraudulent contract they submitted to the DMV. I talked to the DMV and no one there can answer this for me. I'm afraid if I'm somehow agreeing to this contract by paying the additional taxes that I'll not be able to pursue them in a court of law to recoup lost funds.