Is there an "as is" contract in writing that says they're not responsible for problems, or is there a warranty saying they are? It's not clear that you're even using a written contract here. What about a release of liability from them?
See a business lawyer for help, since this is a big transaction.
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Get insurance for your new car. Take your paperwork to the nearest Secretary of State's office or currency exchange and get plates and see to the transfer of registration. You will probably have to show proof of insurance. Congratulations on your new purchase.