Legal Agreement for Road Accident

Hello,

I had a road accident, then the police just recorded that as a fault of mine, so based on a verbal agreement with the other person, I need to pay the full amount of her car as agreed, so need a legal agreement stating those points and stating that after paying the specific amount as agreed by both of us then, there will be no additional payment or anything and the whole case to be closed and she should not require anything more in the future and should be signed and agreed by both of us.
Need that within 24 hours time.
It is based in Australia, so expect that it should meet the Australian Laws.

Kind regards