GOOD LUCK,
It's been about 8 years since I in participated in my last Tri. The ones I did were around the same length as yours. It really is the most satisfied feeling when you complete the course. Everyone was always so supportive. Even the people that were the first to finish, hung around the finish line to cheer in all the competitors.
You'll be hooked after the first one. It's fun to compete against yourself and see the improvement that you can make.