Jim007,
Guess it is a bit too late now but there are a bank of computers that are provided by the GTAA close to the walkway from the Sheraton Gateway hotel. These computers allow you to check yourself in instead of going to the check in counter and since you have no baggage you will burn through there. The participating airlines are US Airways, WestJet and a few others.
Very quick and convenient. I used them about a month back and I was through well before many people who came a long time before me. They are pale green computers that are like the ones Air Canada has. Hope this also helps.
Cheers.