I have gone from US to Canada both by boat and towing a boat with a car
a couple of times and had no big problems. I have friends who do it
almost every year. no biggie. I am not sure exactly where you are
crossing but if you get a guide/cruising book, it should tell you when
is the best times and what the procedure is all about. Some places
might be awful, but that has not been our experience. Best of luck.
Now ask me about crossing the border in a van with a Chicago Blues
Band, well that was another story altogether