Hi Megan
I agree with the above comments. It can be useful to use an agent - though in my opinion, if you research it enough, and you know which VISA you need to apply for, then there is no reason that you will not be able to do it all yourself.
From what I looked at Agents, are VERY expensive - My dad told me avoid at all costs, as they are basically just a rip off. Each person has their own opinion, but I'm doing it myself, and with the helpful advice from this forum, I'm finding the whole thing pretty straightforward at the moment. (I'm yet to submit my actual Visa application, but I have filled it all in, ready to go, and it was all very straightforward)
I'm just one example, and obviously it gets more complicated with an entire family, with kids, trying to make the move to OZ.
Hope this helps.
Cheers,
Stu.