Gettysburg was, by American Civil War standards, a massive battle. It's importance should not be downplayed. But it is also just a part of a larger mosaic of the war. There was great interest at the time in its outcome, but I doubt you'd find anyone in 1863 that would have called it a turning-point.
Smoke n Booze Duty Free currently has 3 locations, Port Zante Cruise Ship Terminal, Frigate Bay, and the new inbound duty free store at the Robert L Bradshaw International Airport. Smoke n Booze is the first inbound airport duty free store in the Federation, and caters only to arriving passengers.
Montreal's airport, Pierre Elliott Trudeau Airport (formerly Dorval Airport) is in the West Island. To get from the airport to other locales in the West Island, you can do the following: take a taxi; flat rate of $35 to downtown Montreal, otherwise about $15-25 to locations in the West Island (plus tip).