[motto]

Make sure that you have your import permit from Canberra before you ship. If the vehicle arrives here and you don't have that it will not be allowed to enter the country. I was surprised to find out that this even applies to trailers. Some years ago I had four ex military trailers on their way before I knew this and had not recorded their details so could not even fully complete the applications. Fortunately due to a shipping delay there was sufficient time to process the paper work and the agent I was using worked a deal to supply the information after the trailers were landed.
It's easy for things to go wrong.
As Lang says - get an agent.
Also as Lang says, AQIS will be your most likely source of trouble. I shipped some new tyres into Tullamarine a couple of years ago and AQIS intervention cost me a $150 fee and necessitated an extra 120 km round trip based purely on the whim of the official I dealt with. His co-worker had already given me the nod to take the tyres but I had to go back for a signature and got served by a different person when I returned who insisted on an inspection that could not be done that day.
It cost $700 to get the tyres from Houston Texas to Melbourne but another $500 to get them off the airport.
It will all cost more than you think.

David