your best answers will be on google..... but from what i recall when i looked into it back in the day, you will be paying way more than 7%. i know for sure youll have to at least pay the 13% quebec sales taxes, and then theres customs fees. They made it alot harder nad more expensive since the dollar hit par to US dollar back in 2008, but now that its almost at par, it may be worth it to you.
as for the warranty, you may want to see if nissan warranties carry over to Canada, some car companies do, but if not, you may have to drive down an hour to plattsburgh to get servicing done for warranty issues
also, a visit to any saaq may help you get more info youre looking for
How to Import a Car From the United States Into Canada | eHow.com