So...
The buyer is the one doing the import, Canada is less involved with the export, but the US side will have to confirm with Canada that it is not stolen or liens or whatever but that is done by the US side.
In terms of how is the money sent/transferred, lots of ways obviously but a certified cheque and visit to the sellers bank for them to deposit is usually safest for the seller and a good location to sign off the papers for title to the new owner.
My experience was with importing into Canada, I had to find a border location with the services on the US side, look up on the web what paperwork was needed and email or fax it to them weeks in advance. (And confirm they recieved it by phone and confirmation email) On the US side they confirmed VIN, inspected quickly the vehicle and gave me export paperwork to bring to Canadian Import border dudes, who charged me taxes and fee for air conditioning.
The import part about bringing it in to Canada is getting the paperwork done in advance for the US side, and getting confirmation that they did receive it, in case the person who received it is not there or forgot etc. There may be some challenges with modified vehicles but you can look that up. Also you will need a provincial inspection for your insurance company within a week or two, I had to have a lengthy conversation with my insurance company to make sure all bases were covered, and got them to email me a paper insurance stuff, you want to bring a plate with you if possible.
Yours will probably be similar, but there are more restrictions for importing into the US.
