Ben - don't worry, whilst the transition area is massive its pretty easy to navigate - there is a well marked route and each of the racks has a very large letter on it and wave start times using it. So all you need to remember is:
1. What letter you racked in (e.g. A, C or whatever)
2. Which side of the rack you were (expo side or non-expo side or if you were C where you were the B side of the D side) to ensure you run down the correct aisle; and
3. How far you were from down the aisle - least important bit really, and I find a coloured towel over the handle bars allows you to a) dry your hands, and b) spot your bike a bit further away.
Then its just a case of remembering that bike out is "expo side by the water" and run out is "expo side away from the water" or just "by the entrance to transition" (there are also very big signs).
You should be fine and certainly spend a couple of minutes walking through it if you have any doubts.