Gone Again,
You also need an ABN # which requires you to register with the Aus Tax Office (ATO). Without this ABN, if you are sub contracting, your client with be forced by law to remove tax at a high marginal rate before you are paid. With your ABN, you invoice your sevices and add the GST to your bill, you do a form every 3 months to give the government the money you collected, and they give you back any legitimite money you spent to earn your living. As your own employer, you will have to contribute to compulsory superannuation (approx 8%) and your own workcover insurance. (approx 3 %) (these are very approximate)
As for public liability insurance, you may have to look into that in depth, the operator will have that insurance for their ops.
If youre out in the bush, all this may be a bit of a hassle, a good accountant should be your first stop.