Excellent advice. I made the trip from Lake Michigan (Milwaukee) via Michigan, Huron and Erie. Entered the Erie Canal at North Tonawanda (Buffalo) Long trip on the canal but lots of nice towns at night. Put the stick back up at New Castle on the Hudson. Trip down the Hudson is OK, not lots of places to stop. New York City very expensive but some marinas will deal for a stay of a month or more. I stayed in Wehawken NJ opposite 40th street in NYC. Good ferry access to NYC. Very rolly marina. $1800 for the month. That was, compared to everyone else - cheap.
Met several boats that had done the St. Lawrence route. They enjoyed it but didn't have much specific advice.
Let me emphasize that if you can go early enough in the season go to Newfoundland if you are an experienced sailor.