All very good advice from kaz, Cooda and gerry, above.
While noting that you seem to be 'fresh off the boat' from UnZud, there's not a real lot I can add, except:
Get yourself a good, standard, relatively low mileage vehicle that's not done a lot of country work.
Avoid ones with lights everywhere and jacked-up suspension.
Prices are good in both Sydney and Melbourne at the moment.
Thoroughly inspect and service the vehicle and run it around for a while before you set off.
Service and, if necessary, re-gas your air-con.
A lambswool seat cover is good for distance driving.
Set it up in the back so that you can doss down if needs be.
Don't have pre-conceptions of how many kliks or hours you can do in a day.
Stop regularly and have a chat with the locals.
DON'T DRIVE AROUND DAWN OR DUSK.
A couple of six-packs in the back is good to have for when you have to say 'thank you'.
A fly-net for your hat can be a good investment.
So can be a roll of toilet paper.
Other than that, have an enjoyable, memorable journey and I hope your gig's successful.
