I went the other way, but if I can offer any advice:
- I hired a customs broker. One of the best $250 I ever spent. They collected the taxes, prepared all documentation, contacted the broker for the bill of sale and other documents. The guy who transported the boat spent all of 10 min. at the border (most of it walking to and from the broker's office).
- There is no duty for any of Canadian or USA boats when moving between the two countries. The only payments you need to make are any state/provincial and federal taxes (if this applies to you). Btw. keep the record of paying these taxes for a long time. Our tax-men came after me three years after I brought the boat. Of course, I had the proof of paying them, but if I did not...
- if you are moving the boat by land, make sure that you have a reputable shipper/carrier. There are many who aren't.
No question this is the time to buy in Canada; you get a 30-40% discount.
Good luck