From one canuck to the next do exactly this
1) Call us customs and ask "when exporting a car to canada which fax number should I fax the title to?" Here's the listing of michigan ports, you'll be crossing in port huron,
http://www.cbp.gov/xp/cgov/toolbox/contacts/ports/mi/
2) Call the dealership you bought the car from tomorrow and have them fax the title front and back to the border crossing here
If you fail to follow these two important steps you and your car will be trapped in the USA. Secondly make sure its not like fort erie in NY where you can only import between the hours of 9am - 5pm m-f. I use Detroit personally because they are forever open! 24/7-365.
The rest is a cake walk. Enjoy the drive.
In 2005 I had my car shipped from Martinez,CA to Windsor, ON with an open trailer. It was $1700, + brokerage fees, plus GST etc etc.