Re: Just finished the Crossfit intro this week...a little nervous
Its natural to be a little nervous anytime you start something new (especially if it is challenging). My best advice would be to just get in there and give it a shot. Remember, one of the many great things about crossfit is that it is scalable. Although the workouts in the "real" class will be tough and you will end up doing things that didn't seem possible you won't be asked to do anything that is truly beyond your ability. Also, I have found that I get extreme satisfaction out of finishing WODs that seemed nearly impossible when I first saw them up on the whiteboard.
Good luck and I hope you have as much fun in your group classes as I have had since I finished the intro classes at my box 2 months ago.