if youre serious about wanting to do good them im sure you dont need to learn the whole course in the next 24 hours, you wouldve worked throughout the year. and if youve worked throughout the year, most of the stuff is in your head somewhere. the more you read the more youll remember.
one of my friends who did the hsc last year told me that the night before a lot of people feel like they forgot everything or that they dont know anything, but once you walk into the exam room and see the questions, you realise you know most of the stuff.
as for notes. the stuff you dont know id suggest writing them out while taking them in. this is the best way to store information, in the exam its also what stands out more. past papers, just look over the questions and answer them in your head if you know em, dont waste time writing it all out. maybe practice the multiple choice online to get you used to the mc q's. i hear they have mcq's for business so yup
goodluck
dont stress
its just hsc nerves
youll do fine. clearly you want to do good. the rest will be effort
maybe you work better under pressure