Question on Courses

I'm from Singapore. I'm now working full time in Australia. But that isn't a question is it. It seems like in Australia, everyone who is in theatre anything has done a lot of courses or gone to University in theatre or something. I have NO qualifications. I can SAY that I can sing and I can certainly SAY that I can act, but obviously without pieces of paper, I obviously do not have anything to back up my claims. (Well, other than someone hearing me singing. I used to busk.) So here is my question. What are courses to take if I was interested in musical theatre? What is the MUST HAVE STUDIED things that meet the requirements for directors to even give you time of day to audition and where can I take these courses if I'm already 25? (I was reading the NIDA brochure. It seems that the minimum requirement to join any NIDA courses is that you be under 20 for some reason) What are the places that are reccomended for inner Sydney where one should go to get pieces of paper? PS. I moved this here because it was on the wrong forum. I still don't know if it's on the right forum yet.