You Go Girl! I just did my first Tri (Danksin @ Disney World - women only), and it was a blast! You'll be hooked after your first race!
Somewhat resembling a sloth, my T1 took forever (4:22 - aagh!)! I put my cycling glove on backwards and had to take it off and put it on again, and fearing my newly purchased $25 open swim mask (it was awesome, by the way!) would get trampled, I had to make sure it was tucked safely away in my bag! I have to wear prescription sunglasses (yes, prescription racing glasses are on my wish list!) and when I put them on they kept fogging up, so I kept having to wipe them with my (wet) hand towel because it's important to actually SEE the road you're riding on... you get the picture! T2 went better because I wore my running shoes (had toe clips) and running shorts (over my swimsuit) on the bike. I'll definitely have at least tri shorts next time (A tri-suit is on my wish list too!). I just purchased some Diadora tri bike shoes (two velcro straps with no tongue) and am putting Look pedals on my bike (a 1987 vintage Trek 560 Pro Series I bought used - it's my best friend!).
Being tired after the bike, I didn't push myself at all in the run - I jogged and walked (OK - WALKED more than jogged!) and took it easy because I didn't want to hurt myself. To be honest, I didn't run any in my training and had only ridden my bike once - my friend talked me into signing up a week before the race (I swim 3x weekly), but trust me, I didn't regret it! I just knew I had to take it easy.
I think it's important to get your heart rate up before the race so that you're warmed up (it also helps your nerves!). If you're not a strong swimmer, you can jog before the swim. I love to swim, so I warmed up in the water. I thought there would be a bunch of girls warming up, but I was actually the first one in the water to swim (some were standing in it). I just pretended I knew exactly what I was doing and swam over to a guy in a kayak to make sure it was OK, and he said that it was fine! After that, other people started swimming too (weird, huh?).

TRICYCLE'S FIRST - TIMER TIPS:

* Find someone who looks as nervous as you feel (goosebumps all over her arms, hands in a praying position, glazed eyes, etc.) at the swim start and wish her luck. It'll make both you and her breathe and feel better!

* Swim start will be nothing less than pure pandemonium (NOT an exaggeration!). Don't worry about putting your head in at first. Once you get going, REMEMBER TO BREATHE WHEN YOU TAKE A BREATH (I'm serious now). Make sure you are blowing your air out (making bubbles) before you turn your head so that you are able to take a full breath before you turn your head back into the water. We tend to hold our breathe when we are fearful and nervous, so you don't want to hyperventilate. That wasn't a problem for me because I love the water, but some of the other girls experienced it.

*practice your transitions at home (I didn't!). You may want to take a little plastic bucket or dishpan to put water (I used lake water) in and a hand towel to rinse and dry your feet before you put on your socks and shoes.

* Reconsider wearing your cycling gloves - if it's a sprint (mine was just ten miles), you may not really need them.

* Stay at your own pace. DO NOT worry about everyone who passes you (they're the elite and professionals, honest!). Try to stay in the easiest gear possible - don't push your legs and make them strain.

* Drink all of your water in your bottle - trust me, you'll be glad you did when you get to the run!

* You probably already know this (I didn't - oops!) but unless it's an ITU race, don't draft!

* Pass only on the left and say loudly, "Passing on your left!" at least twice. One girl I came up on was actually riding on the left side of the road (always ride on the right), but I didn't pass her on the right. I called out, "passing on your left!" and waited until she moved over to go around.

* Take carbos to eat after the race - I like bananas & bagels. My bottle of gatorade (classic fruit punch!) tasted like nectar from the gods and helped me recover. Also, don't stand still; keep walking for at least five minutes after you finish (even if you don't feel like it!).

* Most of all, don't try to go at "race" speed. This is your first one, so take the time to enjoy it!

BEST OF LUCK!