Whiplash

Hi all! I am a citizen of Aus (born and raised) but my girlfriend is from the UK and is currently here on a working holiday visa which will finish up August 2017. We are looking at doing the 801 onshore Partnership visa (and 820 so she can stay). We have booked a consultation with a Migration agent and were a bit taken back by the price and on further research a migration agent looks to be a bit expensive especially considering the visa itself is expensive. I was just wondering how easy it would be to go about going through the whole process without an agent? I'll provide any extra information to help clarify anything. Your help would most appreciated! Thanks :rolleyes: