I've incorporated a number of companies in BC and the process has been simple enough to do on a self-serve basis. After a quick search, I found the following site for incorporation in Ontario, http://is.gd/eDJP - it looks the same as what I went through in BC. The big thing you'll have to deal with in Canada is the GST as you'll likely have to remit on a quarterly basis, so you'll need to watch your cashflow carefully.

Dealing with American customers is largely a matter of choosing whether to accept payments in US dollars directly or do a currency conversion with each payment before it hits your bank. I'd recommend caution with this one as some banks will hit you with a currency conversion fee and give you a crappy rate, so a good payment provider may help in this area.

PM me if you have any other questions.