I brought my car in from Sydney, so I can answer your questions.
As long as the car in question is currently registered interstate, all you will need to do to transfer the registration into your name is take the car to either Regency Park or a place next to the Sturt Police Station for a vehicle identity inspection. I wouldn't recommend taking the Regency Park option though...
Regarding having your car defected during an identity inspection, it all comes down to how lucky you are on the day. I have heard of a number of people being defected, however my car went through without a problem. I had a 97db exhaust (keep in mind they inspect your car inside a tin shed), turbo timer, A-pillar guage and a number of other obvious defects. All they picked up were my tinted windows (even though they were down for the inspection), for which I received a 'formal caution'. To this day, I'm still not really sure what a 'formal caution' is. The caution did require a fair bit of sweet talking however. On that note, I would recommend you find out where all your engine numbers etc are so that you can point them out to the inspector. You might even want to give the numbers a bit of a clean so that you can clearly read them. You want to minimise the time the inspector spends under your bonnet. Also, be nice and talk to them about the weather or something. It'll help.
If you are unlucky, then yes, you will be sent to Regency Park for a full roadworthy inspection. If you don't want to take the chance, remove the obvious defects and you should be fine. I have never heard of anyone actively searching for defects during an identity inspection.
And hey, it's easier than buying from Japan...