Hi vjnr,
I was in your boat and passed my specialist skills assessment and did well so it was valid for 3 years (thank god) because it took me another 2 years to get to my assessment day. I was not good enough in mathematics from school so I took a course to bring me to the correct level that was available on open universities. It was really hard to get a direct answer as to which course to complete and I wasted 6 months doing the wrong course based on bad advice from DFR. I eventually spoke to a great officer at DFR Perth who really helped me choose the right course, but it can be funny. I have a bit of knowledge about what is acceptable, if you want more info PM me with what you need to complete and I'd be happy to help direct you.
I started the whole process when I was 23 and now I'm 25 and sitting in the distribution pool with a strong recommendation waiting for an offer, so don't let it deter you!