I agree, Have a good think about whether driving is the cheapest option.
If you decide to drive its not a bad drive. 4 days is plenty if your aim is to get to your destination without enjoying the scenery too much.
Make sure you have NRMA cover for breakdowns.
Only drive during day light hours.
Check the road conditions prior to leaving and speak to the BOM to ensure you dont end up spending a week or so in Mt Isa or some other god forsaken town due to flooded roads.
Work out early in your trip the fuel consumption on the highway while you still have plenty of fuel options and then check the distances between stops. You may need a jerry can or two. If you can do 400kms you should be fine.
Dont pick up hitch hikers.
Take plenty of food and water in case you break down. A phone with next G should do the job and a computer with next g mobile coverage is excellent as well. (check road conditions, weather, fuel prices)
You should be able to average 100kms/hr all the way to Kununurra.
Its a pretty cruisy sort f drive with long periods of nothing in between.
The roads are generally good, there will be area with rain damage now. watch out for wandering stock and kangaroos and emu's, especially early morning and later in the day.
I personally cover around 1500kms a day when I do thesae type of trips but if your not used to long times behind the wheel that my be way too much and being tired is not on. Stop and enjoy the country, have a beer in the closest pub and a good sleep and try again the next day.
Once you have done it once its no big deal, just a bloody long way.