Many people get confused between an ABN and registering a business NAME. They are two different things. Its often discussed, and its always misunderstood. At the moment you would definitely have to register your business name. Which unless its you that's registered it, you may run into trouble as the name is already registered in Victoria.
There is a huge amount of free business advice from various state departments,and in Queensland (where I'm from), the place I had to register my business name, helpfully provides a huge amount of free business advice.