You'll want to set up a bank account specifically for your business. If you're selling through ebay or anywhere for that matter (your own website etc.), you need to decide on which kind of payments you want to accept. That means you might want to consider getting a merchant account for online transactions (lots to consider here). Or you might want to just go through a service like Paypal who are the middle people and allow you to use their merchant account for a higher fee. Most merchant account providers require a minimum amount.
A budget would also be handy so you don't go over board and you can compare this to what you've done and what your goals are.
I deal with a service internationally, so I don't have to deal with any of the legalities of import export, or tariffs and customs, or shipping. All these should be taken into consideration and accounted for in your transaction. Do you want to include the costs in your pricing or do you want to add on the extra fees to the price tag? Will you be shipping internationally, or sticking with Canada or North America?
A lot of this info can be found on your provinces business site via the government of Canada.
An accounting package will be useful, and I don't know how much business you're planning to do, but a POS (Point Of Sale/Register) might come in handy.
If you're going to do business anywhere else other than Ebay, you will also have to consider marketing, for which you'll have to budget.
Step by step.
Sorry I cant' help you more on the import export thing, but maybe there's someone out there that can?