I'm going to butt in on teh thread too and offer some advice.
I just finished my first ever triathlon (and I'm on such an adrenalin buzz!!)..just the sprint distance (750m swim, 20k cycle, 5 km run). Did it in 1:23:53, which I'm thrilled with, as 9 months ago I couldn't even run up a flight of stairs, without feeling like I was going to die!!
I'd suggest swim and run one day, then swim and cycle, then cycle and run - alternate like that and try to get a few full practises in before the real thing.
and of course eat a good paleo brekkie!! (i had steak and nut bread!! yum yum) ... I just wish everyone would go paleo!