OH so he be like Dick Cheney VP type WHOA
Not exactly.
The current Australian government is a coalition of the Liberal Party of Australia and the National Party of Australia. The Liberal Party has more seats in Parliament, and so the Prime Minister is the Leader of the Liberal Party, and the Deputy Prime Minister is the Leader of the National Party.
If something happened to the Prime Minister, the Governor General would immediately appoint a 'caretaker' Prime Minister. This would almost certainly be the Deputy Prime Minister, but it doesn't have to be - it isn't automatic.
As soon as is practical, the Liberal Party would choose a new Leader and he or she would take over as Prime Minister at that point.
When Prime Minister Harold Holt (Leader of the Liberal Party) disappeared without trace on the 17th December 1967, it was two days before the Governor General asked his (unofficial) Deputy Prime Minister, John McEwan (Leader of the Country Party - forerunners of the Nationals) to serve as Prime Minister. Because of Christmas, it was the 10th January 1968 before the Liberal Party was able to choose John Gorton as their new Leader, and he became Prime Minister.