First spartan race

47 y/o male, I Decided a couple of months ago to sign up for a trifecta weekend near Dallas in October. Being who I am, I signed up for competitive age group. Maybe good maybe dumb. A little bit of back ground, I have done CrossFit workouts for about 5 years and started running more about two months ago , I am up to 4 miles, 10:30 pace. Any tips for this old man. I am getting nervous.