Can't speak for Perth specifically but in most of Aus that I know of you can go to a GP (less than $80 or some places bulk billed) express your interest in an assessment and they'll point you in the right direction! Whether it's who to see, where to go, what to do etc. they'll help you out and (if they're a good doctor) give you an outline and roadmap of expectations and questions. If there's something different about Perth though, I'd love to know :)