There will be many others doing the same thing. In my first duathlon I got passed by an old lady on a mtn bike (and I was on my new road bike). I felt pretty good about myself right then. Tried like heck to catch her and couldn't. You'll be just fine! Just go out there and soak up the whole experience. Smell the smells, really be in tune to the race environment and savor the fact that you're out there doing it. You only get one first triathlon, so have a great time and don't worry about time, place, bike, etc. Enjoy the day- there will be plenty of time for PR's later!