I've dealt with a few pilots such as yourself who had a gap of many years. Skills in flying the aeroplane (especially if a type previously flown) come back readily. Knowledge refresher you can largely do yourself. There'd be many new things and stuff has changed - your instructor can guide you through this.
I'd start by seeking a suitable instructor and ask him/her to outline a plan tailored for yourself with a guestimate at how many hours and briefings would be anticipated.
Don't regard it as a test - just refresher training to where the instructor can tick the boxes per the checklist in
https://www.casa.gov.au/file/105051/download?token=GCyOaRNt
This stuff is only applicable to the USA but illustrates the sort of things that have changed in this time:
Lapsed Pilots - AOPA
Not sure if I still have some relevant info on my PC for one of my recent lapsed pilots, will check later.
A few things that come to mind are:
Part 61 licensing rules - plenty of guides on CASA's website
Radio calls at non-towered airports - see the two CAAPs in 166 series
Class D instead of GAAP airports
AVID or ASIC
Electronic flight bags - see Avplan or Ozrunways - decide on this early as if you have the hardware then it is worthwhile - will save $$ compared to buying paper ERSA and charts etc. Both have a free trial. Flying school may want you not to use it and instead buy all the documents and paper charts - long discussion perhaps, including flying schools Ops Manuals etc - my view is that you will use it in future so start with it now.
VFR Flight Guide - don't buy it, save your money and read it free online.
Have fun.