Parts wise I think you are better off ordering it from Japan or America, depending what you want.
Tune, I can't help you there, not from Sydney, but cheapest would be UpRev Tune. Reflash ECU and good to go.
Brakes - try Nissan 4x4 wreckers, I got a set off a 370z from them. I was lucky, the car was written off and only done 21k kms?
Headunit, there's a pinned thread about it. Someone in Sydney can do it for you.