Off Road for the first time

Tomorrow, I'll be participating in my first off road tri. It's a low key event put on by the Pikes Peak Triathlon Club. I don't even own a mountain bike. I'm borrowing my friend Glenn's. The promise was to have it cleaner upon returning it than when I borrowed it. I rode the course 2 weeks ago. Not very technical. One steep technical downhill. The goal there will to take it easy and not crash. The swim is approx. 700 yards. The run is 3+ miles (subject to change I'm told) on gravel, sand, trail and water crossings. I'm just going to go hard from gun (except for the steep technical downhill) and see what happens. I'll update with a mini report once I complete it.