I'm by no means a tri expert, but you have to go for it if you are thinking about it!! You obviously are fit and can handle the distance. Doing my first one was scary, but only because I didn't know. Now I get butterflies, but because I'm excited more than scared. If possible, try to find a race in your community that you can bike and run the course ahead of time so you'll know all the turns, twists, ins and outs. And remember, that at every tri, there are people there doing it for their first time, too, so you'll never be alone in losing your "tri virginity."
Go for it!!!!