The Buffalo office usually takes from 5 to 10 months after they get your application, but sometimes it is longer. If they want to interview you, it will probably be in New York City. Quebec doesn't usually do interviews; they only do sponsorship approvals. If there is going to be an interview, the Buffalo office (or another office in the U.S.) will decide.
I think if they decide not to do an interview, they will next ask for your passport. Then you have to go out of the country and come back in to be an official PR. You can just drive over the border and immediately return. There is a way to do it at a passport office, but it is usually easier and faster to go to the U.S. and return to do it at the border unless you are far from the U.S. border.