Guptar,
No such luck if you are going direct you need to depart from a customs airport.
I'd suggest if you want to go from your Ballina departure then call in at Lord Howe and clear customs there, it is quick and efficient. Also means you can pick up some extra fuel as Norfolk can be nasty at the wrong time and your alternates are Tontouta to the North and Bay of Islands or Auckland to the south.
Remember you will need the following
General Declaration
Helath Declaration
Cargo Manifest
Passenger manifet
The first three can be combined in one if you google the ICAO General Declaration. Just attach a Pax manifest to it. Also you will need three copies, one for the departing airport, one for the arrival airport and one to hold for 30 days.
Id also get copies of the approach plates for the alternates.
you should enjoy yourself but just remember Norfolk has some of the worst sea fog I've ever seen. If you get a whiff of it go to plan B