Yeah I definitely agree with Susie here,
I won't lie, it is very hard. But its one of those things where you have an "aha" moment and everything just clicks into place. If you're anything like me you'll spend the first 3 terms confused out of your mind, but I picked up a copy of E.H Carr and just read the whole thing ( Which I would seriously recommend if you want to know what you're going to be learning about for the next year) and everything snapped into place - i went from getting 30/50 in my half yearly to a perfect 49/50 in my trial. History extension is just one of those things you have to knuckle down on a bit, but its so worth it in the end. If you're coming first in ancient you'll love it - its all about why Herodotus, Thucdidydes, Plutarch and Tactitus wrote the way they did, how they tainted the "history" of the Julio Claudians, what sociological and psychological factors caused them to write the way they did, how has that impacted on our past and the way we see ourselves. Its honestly such a fascinating subject you just have break through the crazy long sentences and convuluted meanings (Read E.H Carr trust me). By the end of it you will have completely changed how you see the world - its honestly the only HSC course that i truly feel has taught me something i can use in the real world. One word of advice is to also consider your english marks, as in extension you are marked on how well you write , compared to ancient where its all about sources and content - so if you're doing absolutely terrible in english maybe give it a second thought - but if you're mediocre dont worry because extension has its own lingo that you can master easily . You also have to be willing to read - I spent the first 2 terms never reading the handouts we where given, which ended up forming a 50cm tall pile. I was really bored one day and just decided to read them all - throwing out the ones I hated / didnt think were useful. This changed my attitude to the course and allowed me to better understand what i was doing. Most importantly, remember that the course is not about the historians - you are not learning about these people to write a biography in the exam. You're learning about them to take their arguments and either agree or disagree with them in the exam to create a strong thesis about your own idea of what history is - is it fiction? Is it a construct? Does it have any worth? Is history true and objective? Is history only for the intelligent? Also, get yourself a list of terms (I have one i can send you if you want) and make flashcards of them right away - you don't want to spend the year hearing all these big terms and having no idea what they mean - language is pivotal in extension.
Anywhoo, Good Luck with my favourite subject!