Everyone no matter which or how many tickets has to pick up their bags upon arrival in Australia as customs needs to be cleared there. As
Comet21 said, after customs, just head for the QF transfer desk and a few minutes later you will be on the bus over to T3. The bus ride is quite interesting for airline enthusiast.
The T3 business lounge has a decent selection of food for a domestic lounge, showers, computers and free wireless internet access.
More here:
http://www.qantas.com.au/travel/airl...unge/global/en