You should have no problems at all, and you probably won't even be slowed down, as long as you follow the advice already given and declare. I've brought all sorts of things in, once even loose cashews from Phuket, I was certain they would make me bin them, but they were happy when I told them they were roasted (didn't even want to look, just took my word)

It sounds as though perhaps you should bring all your shoes with you and tell them you've been walking in mud, since it appears that you will be given a high standard shoe-shine service courtesy of the Australian taxpayer

I'd like to put to bed the rumour that Melbourne is the coffee capital of Australia - you won't get better coffee anywhere in the world than you will in Sydney, just avoid chains. Any little cafe anywhere in the city will make the perfect cup, it's enshrined in State law and inferior baristas are taken off to re-education camps. This doesn't apply to the city of Newcastle for some reason, where coffee is consistently rubbish.

Curious as to why you would want to bring instant coffee? Of course, if Nescafe really is your preference Melbourne may be a better place for you ...