Hi!
I haven't been been to Helsinki or Finland..but I have several finnish friends who came to my CSU (California State University)...but we all know that Europe isn't cheap. Since it's the Capital, it would be a bit expensive. I know that if you like seafood, it will cost more over there.
Here's what I know about Finn's so far by hanging out w/ them. They're very nice people. But, I don't know how life in Australia is, but in California, or the bay area, where I live..it's common to smile and say hi to everyone. In Finland, forget it! It's uncommon, and my friends have told me people will look at you crazy. Ha ha. But just be prepared for those akward moments of silence.
Almost everyone speaks or knows english, so I don't think you would have a problem. It would be nice to learn finnish, but just learning some words were kind of crazy for me..crazy as in funny. In my opinion, whenever I hear the finnish language, it's like their singing to eachother. If you have any other questions or doubts, I can have my friend e-mail you or something.
But, I think you should take the opportunity to study abroad! It'd be a great experience! I'm actually going to study abroad in France for a year.. nervous but excited!
I hope this somewhat helps! Best of luck!