Let's see... my first event was a duathlon... in March (?) of 2005.

It was uummm... (if I recall correctly):

2 miles running
10 miles biking
2 miles running
10 miles biking
2 miles running

What do I wish I had done differently?

1) More cycling OUTSIDE. Riding a spin bike isn't the same thing.

2) Had worn clothes that were easy to run/bike in, without having to change clothes.

3) More bricks! I didn't do enough ride to run combos in my training.

4) More running! I should have been running 15-20 miles a week, not 5-10 miles a week.

Well, good luck, you have enough time to train- you should do great!