If you're coming from a solid running background, (marathon or even half marathon) racing an ODTri as your first tri should not be a problem. By all means do a few shorter races before Mooloolaba if you can, but if expense, opportunity or other factors prevent you from doing so, I wouldn't lose sleep over it.
Sure, you will improve with experience in triathlon, however there are numerous sources of info (books, mags, Transitions, CR, etc) regarding how to prepare for and race your first tri, which will minimise the chances of any major mishap. Like seriously, what is the worst that can go wrong? If you think ODTri is the challenge for you, I say go for it.
My first tri was 1.6/30/11 or thereabouts (can't remember exactly, it was 1985). Back then, most triathletes debuted at similar distances, because the only other option was to race something longer. "Sprint" triathlons in those days took your average competitor 2.5 or 3 hours. Now the sport is far more accessable to a broader section of the community. Certainly, that's a good thing, however some newbies prepare at length and with consistancy to complete the "enormous" task of their first triathlon, only to cross the finishline with a feeling of "I should have raced weeks ago, I was ready to be a triathlete then!" or "That was over in a flash, I should have raced the longer event."
My favourite debut triathlon story is that of Uncle Dave. He chose the Sri Chinmoy Three Day Ultra Triathlon as his first triathlon.

15km swim, 400 cycle and 100km run, contested in a stage format, so you could grab some rest in between disciplines. If you weren't too slow. A few weeks later Dave was set to back up for his second triathlon, an Olympic Distance race. A few days before the ODTri, my phone rings and it's everyone's favourite Uncle, now a hardened triathlete with over 500km of triathlon experience. "Hey Paul, what do I have to do in the transition area?"
But to the original question from Mackatelli? A pair of tri knicks is a good bet for the event. They will minimise the risk of chaffing and you won't even notice if they are wet on the bike and run.