Let me state beforehand...proud of you for getting into triathlons and getting into shape. Ultimately that is the best goal.
Now, be careful trying to over-reach your goals. This being your first one you should go in with realistic marks in mind. My first tri was an Olympic. I had LOFTY goals of finishing in 2:30...NOT! I finished in 3:07. Sure I was dissappointed but once I realized that my goal was shot I began thinking about why I couldn't reach them. Naturally it all came down to the way I trained and the amount of time I had leading up to the race. I adjusted my training and last year dropped a full half hour off my time.
So, set very attainable goals for yourself. Follow your schedule. REST on your rest days. Drink water throughout the day. Plan days to do a brick workout. Practice the transitions. Listen to your body. Practice with your nutrition. Stretch after you workout. Most of all...have fun. Make the first event a fun, learning event. If you have a chance, go watch a race before yours to get a feel of what all goes on.
Good luck,
Fred