I can help with that

So just so you know from the get go, the degree forces you to undertake a mathematics minor for your science degree.
Because Computer Science encapsulates such a broad range of topics, a knowledge general computers/programming is really beneficial, but you can still do it without the background.. First year they will start you off with FIT1040 - Programming Fundamentals and FIT1029 - Algorithmic Problem Solving, both of these units do not assume any prior knowledge to computers, algorithms or programming, if you're coming into this degree you should really really focus on nailing the concepts with FIT1040. In the second semester you undertake FIT1004 - Intro. to CompSci. I'm doing this unit now, and even with a programming background it is a bit of a killer. You'll do heaps of programming across various languages so it does have a pretty steep learning curb that I don't think FIT1040 completely prepares you for. Ultimately I would say that if you could get a programming language done it would definitely help you in the future.
The science component varies quite a lot in the major/minor that you pick. With this degree you have two choices, major in mathematics and minor in something else or minor in maths major in something else. I'm still undecided as to what I'm going to major in, but I'm learning more towards Maths at this stage. Most majors have a starting point so that anyone can pick it up but you should really check with other students for that. Geoscience is awesome as it's not in the VCE curriculum they have to teach you from the very beginning.
Let me know if there's anything else I can help you with.