Olympic tri this weekend, and I'm not prepared. Advice?

I am in a pickle.

I am a swimmer, and have been competing for my whole life. I just finished my first year of college level D3 swimming, and I've done a couple sprint triathlons over the last year. I finished high/first in the swim portion, middle of the pack in the bike, and lower third in the run.

When my bike tire got a flat early in my first triathlon, I was too jumped up on adrenaline to just give up, and so I got out of the way of bikers and finished the bike section on foot : a total of ten miles. Which was silly, but a serious Ironman triathlete I spoke to afterward convinced me that I would be okay signing up for a Olympic level triathlon if I had the mettle to get through that ten miles without training for it.

So I signed up for one, and added more running and biking training into my program. This only kind of worked, as I constantly,  no matter the amount of running I did, got some serious shin splints that would hurt for a long time afterwards.

In addition to this, my swim coach has been sending me weekly swim workouts, and so I've been obligated to get these done before thinking about my runs or bikes.

So I'm not worried about the swim or the bike, but I'm wondering if anyone has any advice on avoiding those awful shin splints. Should I take it easy on my first two legs and just hope to complete the whole thing, or can I give it my all and attempt to be competitive? What should I know about an olympic as opposed to a sprint?
I'm pretty much set on doing it even though I have almost no run training, unless you guys give me some really compelling reasons to abstain. I am very dedicated swimmer, and I have a great attitude about these kinds of things... which was enough for sprint triathlons, but I do understand there comes a point where you definitely need more than just a can-do attitude.
I have other questions, but I'll see if anyone responds first.
Thanks in advance, guys!