You will do FABULOUS!! I just know it! And FWIW I still get nervous before *any* race, no matter how small or how many times I've done it. I think it just comes w/ the territory..
My only advice is this... As you are coming to the end of each disclipline get your mind into what you need to do as soon as you hit transition. Do a quick mental run down and start preparing yourself for it. And on the bike don't forget to soft pedal or spin the last 5 or so minutes. It helps w/ the legs for the run. And when you hit the run you WILL feel like CRAP for the first 5 minutes. Just realize it's coming and run through it. It really will pass and you will feel so much stronger for gutting out that rough patch.
But most of all HAVE FUN!!!!! That;s why we do this, right???