2000 Saturn L100 could it have been turned off in error?

Air Conditioning problem
2000 Saturn L100 Automatic 200k miles

LW1 stn wgn:
My a/c worked fine until I had my car checked over for a road trip in January 2006. When summer arrived, hey no ac! I've not really needed it til this year, 2010, and am afraid of the cost. Where should I go in Toronto or thereabouts for a check on the ac and what should I expect to pay?
Thanks, Wendy.