My First HIM

Just wanted to get some thoughts on the overall tri experience from training through an event.  I am 32, have an athletic background, and a strong desire to not only finish my HIM, but also to compete. 

My main downfall is my limited tri experience.  I have only done two. (a full xterra, and a sprint).  I had never been on a road bike until the day of my sprint.  I did not know what to expect, so decided to set a goal of 1 hr 30min.  The distances were a 400m pool swim, 15 mile bike, 5K run.  I was way off of my goal because a flat that cost me an extra 40 min because I did not plan on finishing once it happened until a friend driving by gave me a tube.  Due to the poor weather, I did not even plan on finishing the race.  Nonetheless, my time would have been 1hr 18min and I wasn't even tired.  I would have beat my goal by 12 minutes.  This was all done with almost no training.  As I said, I had never been on a road bike (one I borrowed from a friend) until the day of the event.  I am (was??) a mountain biker. 

I will be signing up for IM Augusta 70.3.  I have made the commitment to take training seriously, even joining a gym.  I have been riding inside, running (on a treadmill to build a base only), and swimming about 1000m twice a week without stopping.  I am not a runner at all and very new to road biking.  I am willing to put in the time and effort. 

My plan is to do an international distance at the end of March, the Xterra in May and a sprint in late August to prepare.  I am looking for some intense training programs to meet my goal of 5 - 6 hrs or less in the HIM.  Being very new to the sport, any advice or personal training experiences would certainly be welcome.  Also, I hear a bunch about nutrition, but have not seen any examples of what an athlete in training should be consuming.  I eat healthy now, but doubt it is what I should be eating for maximum performance.  Any suggestions / advice?  Thanks!!