You'll need a work visa, I believe. Changing citizenship isn't horribly difficult, but you have to drop your US citizenship to do so. You can't be a dual citizen except in certain cases (like me.
).
Getting your citizenship will take a little while, and cost some money. I don't believe there is any benefit to being a US Citizen living in Canada, except you don't lose your US cit. I believe that if you're not a citizen of Canada, you can't use their free health care, though.