Are you planning to go 'clockwise' or the other way, and visit Queensland first.
The reason I ask is because of the weather patterns you will / may encounter.
Anti-clockwise, may give you tailwinds across The Top, and get you out of the 'Wet' quicker - i.e. before the larger CB's become an 'everyday occurrence'.
They 'usually' get bigger in Jan. - Well around the Kimberley anyway....
Take plenty of water, probably 3G net for your mobile, and heed what has already been said re fuel etc.
The rest of the flight south from Port Hedland, then, should be reasonably pleasant, the only real problem here is maybe encountering a 'West Coast Trough' which will involve some CB activity at around that time of the year.
But then you have the choice of going 'coastal' via Carnarvon, or 'inland' via Newman.
The inland route can be very 'bumpy' due heat turb - but you will have that worked out by then.....
Should you decide to go the 'clockwise', then most of the above will still apply, but you may be 'deeper' into the 'wet'....
Listen to the local operators, and don't be afraid to ASK them if there's anything you need to know. You will find everybody very friendly and a wealth of 'local knowledge' - so ask as you go, is my tip.....
For fuel across the Nullabor, PHONE first to check where its available, and how much etc - be prepared and plan accordingly. Although Kalgoorlie - Forrest might be 'the usual' route, I can say that Caiguna Road House make the best bacon sandwiches and you can taxy right up to the bowser - but phone first.
Take the faster aircraft if you have a choice - you'll still enjoy the trip and won't appear to be 'standing still' over the more flat 'uninteresting' areas (?)
Cheers and ENJOY. Don't forget the camera....
p.s. Stand by for pages and pages........
