I'm definitely siding with everyone else here, get your cash back... you've had enough of this place.
When I went to shop for my new car, I found this website:
http://www.carbuyingtips.com/
Great tips, and in there the author even said: DO NOT GIVE A DOWN PAYMENT IN CASH!
And if you signed papers on this deal, it will be EVEN HARDER to get your cash back!
They absolutely owe you your money back, and you should not have driven around a new dealer car.... I would be pissed if I knew someone was driving my new red Versa. Why? Because it's now USED, no matter how far under 100 miles you drove it.
Read this guy's website, then contact your local better business bureau to see if there's been a complaint filed against this dealership. Grab your contract, your receipts and call your Attorney General's office to register a complaint if they give you a run around.
And please, be careful with your money. A sucker is born every day, but you don't need to be going to dealerships in a crib.
Print out a Nissan ad with everything you want in a car, slap it down at your local dealer and say "I want this, do you have it?"
That's what I did, and I got the car I wanted a week later (they were getting the delivery in, the only reason I'd take a car that is either not on the lot or not ordered by me from the factory.)
Also, NEVER take a car from another dealership. You lose all bargaining power, and certain incentives to make a car cheaper. Find out what dealership the car YOU want is coming from, GO THERE and BUY IT. Plain and simple.