Exchange US dollars

Right now the Can$ is roughly 0.81US. You have to declare over $10,000 at Canada Customs. So $12,000Can is about $9,600US.
Banks here will add a service charge to convert usually 2.5%.
I would call a bank to find out.
I stayed at the old holiday inn on grand island many years ago while
Xmas shopping on black Friday.
I could be interested in a face to face exchange for some of it for trips south but it all depends on where you buying the car. Good luck with your purchase.

Denny