Shonfield,
good thinking. Given some of the post on here about recruiting you are safer allowing a lot of time for lost paperwork, incorrect info and a slow process.
What you provide is what they will use but no doubt you can update this info.
The first part of the process after recruiting is to get a spot on an FSP course. All the info you provide is looked at and you can update this when you have new stuff. Unless you have finished YR 12 than you ATAR will not be avaible and therefore does not help in getting an FSP spot.
Good luck