Sorry, can't help you with that one. The best thing I can suggest is getting in touch with an AME and ask this question there. But I'm sure someone else will pop in with a better answer.
The licence itself is a familiar scenario, long expired ratings and such. The head of training or similar at the ATO can evaluate your situation, specify what training needs to be done to get you up to speed (very little most likely seeing as you've been flying on the AUS licence) and organise a prof check. You may need to sort the medical situation by then though. After that its mostly a complex paperwork exercise, but the ATO should be able to help you with that.