I know this is a few years after your postings but I have recently been tracing my family's history and found I too am a decendent of Guillaume Couillard. Just like the previous poster my line goes to Francois Bissot. From there I am a decendent of Louis Jolliet and his wife Claire. I would really like more information dating back further if anyone has it or knows were to get the book previously mentioned. Thank you.
P.S. I read online that almost all French-Canadians are decendents of Guillaume because they had 10 children.