Do it. Anything you do to prep for it will be beneficial for your health. I want to do something like this too, and the best term I can use to describe my mentality is "tourist". Sure, I will go and compete, but since I know I won't be competitive, I will just plan to enjoy the experience of it all, and being in the middle of it - just to see what it is like. I'll try hard and enjoy the accomplishment, no matter where I place.

Then do it again next year...and the next. See how you improve.