This I can answer... We received the email from Canada Immigration 6 weeks before the date of. The email was very specific in what to bring. You may get different instructions but it seemed pretty standard to me. As for changing the date, it said it was the only date avail to attend at the office - that part was in bold; so...
Not sure if same building, but Canada is on Winston Churchill Ave
Thank you LL. Six weeks is not enough time to get a decent price on an airline. Gotta do what I gotta do!