I say go for it too if you've got the determination/motivation. It will be tough though, especially if you try to keep up with more conditioned riders. You'll need to pace yourself carefully. Stay well hydrated and eat a 'power' bar(Snickers?) every hour for quick energy. Load up on carbs the day before to maximize you glycogen stores.
Fit is first. If you try to do this on a bike that doesn't fit you well, you'll really pay a price. For maximum pedaling efficiency, position the seat so that your leg is slightly flexed when the ball of your foot is resting on the bottomed out pedal.
Good luck and let us know how it goes.