Hi,
I did this 2 years ago with Sydney Aviators (I think they share the fleet with Basair).
CoV is not an issue. You can request it already from home and receive a preliminary license via E-Mail (i think it is valid like 3 month?) and the original sent by post to your homeplace within a few days. This should all be sorted out before you even depart.
The ASIC is more annoying. Also there you can (and should) send the application already from home, at least 3 month prior to your departure.
However, the final checks will only commence once you are through immigration (do not forget to give them a call the day after you arrived) and only then print the ASIC, which is done by a contractor. This normally takes 10-14 days.
During this time you can already do familiarisation with an FI or do the BFR, however you need the ASIC before you want to fly around alone. (Well theoretically not all airports require the ASIC, but practically everyone with fuel does.....)
Maybe this thread also gives you also some ideas on where to land:
http://www.pprune.org/pacific-genera...w-qld-vic.html
If you have more specific questions, I am happy to answer here or via PM.
Regards,
Florian