I agree that prep is the key to success in this assessment (the version of the 5 P's I know is the 6 P's - P*ss poor preparation precedes poor performance!). On a recommendation I bought a book called GMAT for Dummies to help me, widely available for a few quid online. It's a bit OTT on the maths but some of the verbal reasoning stuff really helped.
For the sim ride I rehearsed the profile ad infinitum using nothing fancier than FS98. I think the key to the sim is not to have to think about calls/speeds etc, get these properly drummed into your brain and then you have capacity to actually fly the sim and analyse what is happening. You certainly get plenty of time to prepare so no excuses really.
As already mentioned, be yourself in the interviews. The interviewers are very pleasant and are not trying to trip you up or bamboozle you. I found the whole process to be far more enjoyable than I had imagined. If you don't get in, don't let it get you down. There will be another good company you may be more suited to.