Prostitution is legalized throughout all of Australia man, no need for concern. Different states have different laws regarding brothels though if you were thinking of going to one. They're legal in Sydney which is in New South Wales but illegal in Perth which is in Western Australia.
Last time I was there was a few years ago but I had a good time at the Star casino in Sydney. Sydney is just a generally cool place, you'll have a great time.
I went to Club 121 which is a brothel near the casino and it was a shithole. I went to another one too called Tiffanys and it was much nicer. I forget the rates exactly but it was comparable to here.
Btw, when they say they do "French" that means BBBJ
Have fun! I love Aussie girls, they have very little of the judeo-Christian hangups surrounding sex, and they love Americans