Yes, we did that excersion a few months ago in St. Maarten and it was well worth the time and money, we actually won by a nose!
It can be a lot of work, if thats what job you want to do, or you can be a "cheerleader", which ever you want.
If you have any questions, just ask, not a problem.
You can sign up for a task thats very little work, or be active, just let them know what kind of job you want. Yes, it can be work, but very worthwhile and a lot of fun, especially if you happen to be the winner, its great!
If this is an excersion you definitely want to do, you can sometimes pre-sign up on the cruiselines web-site, depending on what cruiseline you are cruising on. We did that, just to make sure we were on, had the conformation included with our docs when they came and tickets in the cabin when we arrived onboard.
Good luck and if you can do, you'll love it. I seem to remember it being $80-90 per person, but well worth it, have fun!