Great question. I think HPross has some great ideas as far as technique wise. I would like to address the more mental part of the situation. Market basket style events can be very stressful if you are not use to doing them. First of all, keep it simple and stick to what you are great at. This will allow you to produce a much better product under pressure if you have cooked it many times before or in a style that you have done before. Stay clean, organized, and calm, a dirty work station produces dirty food. You have 30 minutes to plan so that is more than enough to figure out what you are going to cook and how you are going to do it. Do not spend all your time on the dish, spend the first 10 minutes on the dish and force yourself to come to terms and move on. Build out a timeline in 10 minute intervals on what you are going to do and how you are going to do it. This way you know if you are behind, ahead, etc... and will allow you to time your plating better. Lastly, have fun and just cook, this is what you love to do, this is what comes naturally, if you let things come to you and cook with passion you will come out with a great product. Good luck, I know you will do great!