Don't miss Ben's Deli downtown for a great Smoked Meat Sandwich.
They're like a Pastrami but smoother flavour and melt in your mouth.
The Metro is your best bet as all the major buildings and centres are all conected underground to it, Montreal is alive down there as well!
You'll have a great time, and if you want rent a car and take a day or longer and see Mont Tremblant famous for skiing, and as a mountain get away!