Kudos to you for taking on a task like this. You can start by reading the rule book which will tell you how to run the competition part.

http://www.modelaircraft.org/files/e...cialevents.pdf

I'd say for a small event you'll need at least 4 helpers at the event. One to help at the flightline getting the next guy ready while one flies, one at the end of the runway to get planes off quickly and help recover crashed planes, an announcer, and a food guy if you're going to have lunch. Having run lots of events at church and schools, I can say that you should try not to have a job for yourself at the event, except maybe announcing and putting the order of pilots together if you can't get anyone to do that. If you are the CD, you need to be available to people on tasks to answer their questions and to contestants to greet them and help them. You'll also need a publicity guy, which can be you if you want, to contact other clubs and put the event on all the internet listings. If you are going to use this to get the public interested, there's also the task of putting up flyers at local businesses and contacting whatever community calendars you have in your area. You might even be able to get the local news to report on the event if it's a slow day and you meet with them far enough in advance.