can't speak for bringing items south, but when purchase from the US and bring north, We just got ahold of our border crossing, printed the paper work and submit and they notification couple days prior bringing to border then once in Canada it needs an RIV (recreational vehicle inspection) prove its road worthy.
I have had very different experiences amongst border crossings. So call the border crossing you intend to use and ask them what they what and how to do it to avoid any headaches