Yes the Canadian GP has assigned seating for practice and qualifying.
I've stayed at a bunch of different places, nothing bad to report, no recommendation either. Book a room ASAP - they do sell out and prices go up as the date approaches. Most places will require you to pay for a minimum 3 day stay upfront.
I've always tried to stay near a metro station so I had easy access to the park.

I've been to both USGP and CGP and hands down I prefer CGP. It's a shorter drive for me and as was mentioned Montreal has a european flavor with great bars/parties.