I'm canadian and my mother in law is US citizen and a few years ago when you cross at the boarder at the duty free you used to be able to get a refund there for the GST or HST that you paid all you needed was the bills to prove you spent the money in Canada and paid the tax, that was a few years ago though so you would have to check that out now. As for bringing it across without telling them and you get caught they can confiscate the camper and make you pay big time with lots of fines that are expensive.
Dave
