What are the chances of me getting caught trying to enter Canada with a criminal record?

I have a felony on my record from 15 years ago and have been squeaky clean since then. My buddy that wants to go had an assault and battery charge (Misdemeanor A) 10 years ago. We're going to fly to Montreal to see UFC fight in April. What are our chances of getting denied entry into Montreal? And do they check everyone? What can we do to avoid this problem?