Congratulations on doing your first TRI - Way to go.
My $0.02.
Don't change NOTHING.
Eat a SMALL Brkfst 2 hrs before race. I eat Oatmeal + maybe part of a Banana. Drink WATER only till Race.
Take a half bottle of water (on the bike) just in case. I doubt you'll need any. While running they usually have tables set up.
Best thing to practice is TRANSISTION - have everything laid out and thought out.
Race against NO ONE - take it at your own pace. Don't get caught up starting too fast. STEADY RHYTHM.
And best of all advice ENJOY IT - your one of the select few who have the courage to do this. GOOD LUCK!!!!!!!!!!!!!