I have to show in municipal court later today. What should I expect?

You COULD go to jail, but it's unlikely. There should be a representative from the Merchant there to testify against you. Otherwise, the case would probably be dismissed due to lack of evidence. IF your record is wiped clean, or even if it isn't, I hope you learned from this. DON'T DO IT AGAIN. If you want something, buy it like the rest of us do.