Australia Visit Visa Required

I m Pakistani Citizen and living in Shenzhen China on Z (Working) VISA / Temporary Residence for last six months, my contract with my current Chinese Company till the end of this year 2012. now in my annual vacations I want to visit Sydney Australia to meet my brother n law / Niece / Nephew, Can I get the visa from Guangzhou ? and what are the supporting documents I need to submit with Passport/Visa Form to the embassy ? also what is the processing time (Approx) to get the VISA ??