Ahhh the long road to CASA...
Have done so in 2006 myself.
1.You need to apply to CASA for an ARN (Aviation Reference Nr) as well as for an AUS ATPL based on a foreign ATPL. Costs +-300 AUD can't remember exactly.
2. With an ARN go to aslexam.com to book 3 exams.(Can'rt remember Costs per exam)
3. You need to first complete the AUS CIRX and CPL Law(A) theory exams
4. Only once you've passed CPL law will you be eligible to write the ATPL Law exam.
5. Once all three passed and AUS Class 1 medical in hand, you can complete a Command Instrument rating on a ME aircraft at any school with an ATO(Approved Testing officer)
Navaid:NDB will be part of the initial CIR
There is an oral exam as part of your CIR based on the Knowledge deficiency report given to you after the CIRX exam. (The ones you got wrong....)
You will need a complete set of the AUS AIP (incl DAPs East and West) Various AUS TAC & ERC charts as well as an up to date ERSA.
Try borrow an up-to date set, as buying it all is a very expensive option and the info is available on the net if you ever need it in future.
Good books to get are Instrument Study Guide form Bob Tait and use as many past papers/exams as you can get your hands on.
The CIRX was the most tricky part of it all. Open book but a lot of cross-referencing required.
Hope this helps
Hobagoas