Spot Financing- Options?

[waxpoetry]

So I made a mistake of taking Spot Financing on a vehicle.
I have a gut feeling that the dealer will not be able to find me financing and will ask me to renegotiate the terms of the contract.
I am in California and under the "Sellers right to cancel".
I was pre-approved with a previous lender but decided to try and get financed by the dealer (my mistake)
My question is:
Can I just take the check to the dealer from my approved lender to pay off the vehicle? Or, will the dealer have some means to not allow this?

[30daylate]

I would be seriously surprised if he doesn't take the money. The reason the interest rate is so high is because a lot of people default. He probably would just want your money.