car dealer wants car back after 17 days, IL

I live in Illinois and I purchased a car from Martin Nissan who said they do not show you a car or let you leave witha car unless you are approved for financing first. I purchased the car on 4/21/08 and signed the sales contract on 4/21. I quit the job I had at the time and switched to a better paying one a week later 5/01/08. I was told that was fine by the finance company citi auto finance and the dealer on 05/05/08 and faxed proof of current employment. I got a call from the dealership today staing cit auto now only wants to finance 25k instead of 28k so I have to return the car or come up with another 3k to keep it. I was told by a friend that the dealership only has 10 days to cancel a sale once the documents are signed and they want me to return the car so they don't have to eat the loss of 3k, yet they want me to come up with an additional 3k after I have had the car for 17 days now. I had to borrow the money for the down payment so if I return the car and get my trade in plaus my down payment back I am still out all the finance charges I have to pay back on the loan I too ko ut for the down payment the first place. Is there anything I can do to protect myself in this situation?

[annjd]

See your other post.