Hi Andrew, Cams L2S is fine, you'll also need to show your current Affiliated Car Club membership card (like SAU VIC for example), AASA is the other option...
It's skid pan with some Timed Back Track work, it's definately not a track day. Youtube for DECA Long Wang for examples of the Back Tracks...
Yes, Yes Yes... Do not have to have a cage to race, do not have to have a cage for passengers, it is not a high speed event... chances are the fastest you'll go on the day is about 130kmh on one part of the Long Wang...
No tyre fitting facilities, the skid pan generally does not chew through tyres too much, unless you're deliberately trying to destroy tyres, you won't need fitting facilities... I'd recommend bringing a spare pair of wheels for the rears if you're planning on driving back to Melbourne and think you'll be finishing a set off.