good luck, I'm in the same "boat" as you. I saw an ad online for a triathlon two weeks ago and signed up, it's tomorrow. So, hopefully I learned enough in these two weeks to do alright. My goal is finish better than half the field and learn as much as I can.
Is the triathlon you are doing an open water swim? If so, try to get plenty of open water swimming, especailly if it is ocean, it can be a big diference from a pool.