I started triathlon after a miscarriage and the idiot leaving me. I needed to know that my body wouldn't fail me. I did an olympic distance which I trained for for 12 weeks, with no running experience, only biking on my banana seat Huffy back in the 70s and not much swimming, 2 times a week, poor technique. I trained with a team for the swimming, improved immensely, from 100s at an average of 1:50 down to 100s with an average of 1:37.
I finished second to last in my first tri, the guy behind me was 72 (I was 37).
Now I am dedicated to the sport and did 3 olympics and one sprint in 2008 and just signed up for VINEMAN, my first 70.3, I am still slow running (10k 60 mins) but I am improving on everything and actually hope that in 2010 I qualify for a championship spot in my age group, which will be 40-44....

GOOD LUCK! and ENJOY, it is really NOT about winning but about enjoying the training, which is way more intensive and time consuming than the races.