That particular test wasn't around when I got my electrical license but electrical inspectors, testing people etc tend to be especially worried about:
1. Maximum demand, voltage drop, cable selection etc calculations. You need to know this backwards, fowards and every other way. And I'd be expecting the questions to be about multiple domestic, commercial and/or industrial installations not a simple freestanding house. Probably a lift, a few motors, some water heaters and maybe even a welder buried amonst the detail just to make it more complex.
Personally, I find it much easier to understand the reasoning behind things rather than relying blindly on the formula. Otherwise I tend to just forget the formulas. Each to their own though...
2. Installation testing proceedures. There's more than one way of going about it and doing a thorough test, but the assessor won't be interested in that. Do it exactly they way you were taught at TAFE - odds are that's the only way they'll accept. Don't make stupid mistakes like selecting the wrong voltage on the Megger, forgetting about the MEN link or the equipotential bond to the water pipe.
3. I'd expect some earthing questions in there somewhere and probably some deliberate "faults" on any set up you are required to test.
Can't really help with the nerves bit, but I'd strongly suggest that you focus absolutely on this - just make AS3000 and AS3008.1 your life for a while and leave the partying until the test is passed.
As I said, I have NOT done a Capstone test, it wasn't around at the time, so the above is just my guess based on own experiences and that more recently with training apprentices (including those who have sat, and passed, Capstone tests).