Automotive Forums  Where Car Enthusiasts Go to Discuss Cars Online

Hello Automotive Forums, I've been lurking the site throughout my car buying experience and have found this site very helpful.  However, I have just discovered that I left the dealership after making the purchase without sufficient documentation and need to make a decision ASAP because of a number of issues I won't go into.

Basically, I agreed to purchase a car based on incentives that require me to finance through the manufacturer.  I was told that we would qualify for the lowest rate since we have close to a perfect credit score.  Above 750.  However,  after signing all the paperwork, we have no paperwork that indicates the exact amortization.  I'm worried the dealer will call us in a week or two and tell us that we did not qualify and that they are raising the rate.  The good thing is that the car has not yet been driven off the lot. I am to pick it up ASAP.  But I do not want to take it until I know exactly what the monthly payments are. What should I do?  What are my rights?  I am worried that if I do not take the car they will threaten charging me for storage or something, but I'm also worried that if I take the car, that means I've accepted whatever.  They tell me now that they cannot give me anything in writing until they process all the documentation which will take 3 weeks.  please advise.
Any help will be greatly appreciated.