This is the relevant document for importing a bus into Canada. http://www.tc.gc.ca/media/documents/roadsafety/vafus.pdf
While there are always stories of people managing to import and register a converted bus, the rules are that it must be completely stock, as manufactured and with a letter from the OEM stating that there are no outstanding recalls, unless it is older than 1971. There are brokers who do this for a living - My bus was imported by such a broker who then had it modified to meet Canadian regulations (mostly putting a speedo head on that read in kph, and putting a kilometer hub-meter on a rear hub). It also got a sticker stating all the weight numbers in kilograms. But I'm unsure what you need to do. In your case you're not really importing it, the buyer would be. I suspect you would have two routes to follow. One is go to Canada with your bus for a visit and somehow forget to bring it home with you. Probably a felony, definitely fraud, and it happens all the time, albeit with smaller vehicles and articles of interest. Second is to get the buyer to do all the paperwork for you, meet you at the border or hire a broker, and do it right. I@N tried, failed, and ended up taking the bus apart for salvage.
I really think the shorter answer is that you can't sell your bus in Canada, you have to sell it in the US. Importing it is up to the buyer. Delivery is a different matter.