customs in Australia or New Zealand

I plan on visiting a friend in Malekula, Vanuatu in October. He said to fly to Norsup. I can leave from either Sydney or Brisbane, Australia, or from Auckland New Zealand. It looks like the most flights are between Sydney and Port Vila, and from Port Vila I'd have to fly to Norsup.

I'm wondering how much time I'll need in either Sydney, Brisbane, or Auckland to get through customs. I'm wondering if I'll be able to make it to Port Vila the same day I get into Australia or New Zealand, or if I should just plan on staying the night.

it would help if you said what time the flight was meant to leave, and possibly where you might be travelling from. Brisbane has a much smaller and more user-friendly International Terminal than Sydney, and Australia is much closer to either country than New Zealand.