im actually applying for Canadian pr as we speak and there is no extra paper work for dual citizenship, Canada just doesn't make you denounce your American citizenship or forfeit your American passport. Good luck finding a reason for them to let you in permanently tho, I just happened to have married a Canadian and we decided to have me move there instead of him coming to the USA
How "hard" depends on the individual. It would be a lot harder for those who aren't Canadian, for those who have no immediate family living there, and for those who have no ties to Canada.
