There is a regular, daily bus service run by Veolia from Montreal to Sutton. It takes just under two hours. Check with the company for details on 1 877 348 5599 but it leaves from the Montreal Central Bus Station at 11am and 6pm returning from Sutton at 7.30am and 3.15pm meaning you can get out to the country for a great weekend of hiking, skiing or boarding. Students get a 20% discount.
You can take the bus to or from Sutton. However, I can't remember for the life of me how long the ride is between Sutton and Montreal because it was so long ago... But I think it was at least an hour or two.