First Crossfit competition and nervous as hel*!!

I am freaking out. By luck, I got a chance to compete at a Crossfit competition this weekend. I found out about two days ago, and will be competing in the beginner's division this Saturday. I already have butterflies in my stomach! Any advice? there is a running wod which is just an all out 800 m sprint for time and im a slow runner and hurt my foot running a half marathon last weeknd (FYI, no training for the half, got a time of 2:31 so was super happy, but the top of my foot toward my ankle has been hurthing).

any advice for the competition??? i dont think i will be able to sleep! ALso, ladies, what pants/shorts do you recommend. There are box jumps in one wod, and i don't like that I have to hold up my capris when I do box jumps at my gym, so looking to invest in some pants/shorts. Thanks in advnace!