Yeah it's possible but it may be a bit difficult as most people prepare for it in a space of 6-12 months.
Your scales are basically the same as your 6th grade ones but with a few more, so you just need to learn and perfect those. You also need to play them I little bit faster.
Sightreading is basically the same, maybe just a tiny bit different
If I recall correctly, I think aural tests actually get easier (at least for me)
As with general knowledge, it's basically just a little bit of research
However regarding your pieces, you will need to practice everyday for hours! You will need to learn to perfect your pieces as much as possible as well as show of your control of the instrument while performing these pieces to the examiners. It may be a bit difficult to both learn and play your pieces an an appropriate level to do well as not only are they new pieces, but they are more difficult than your 6th grade ones.
I would probably advise against preparing from scratch with only 2 months as it may be a bit stressful and at the moment, you don't know how hard it is. The reason that people follow AMEB grades is to slowly learn how to 'master' their instruments and learn about the different things that it can do. If you race through your grades, you may miss a lot of this learning.
