Laura,
I was just going to suggest what Bev did. The show sites are usually chock full of information. The show that I have gone to all allow cake dummies unless you are entering a sculpted cake.
If you decide to enter I am sure you will do fine… hey the first time i entered a cake into a show I took 1st place and the division. You never know what can happen :) Good luck if you deicide to enter!!!