listen to wendy, this is what i did too
with modern its really easy to get overwhelmed by the content, but there is no need to freak out
yes, there is a lot of content. yes, you will need to learn alot of it.
however if you break it up into small pieces and know your strengths and weaknesses you'll be right!
i spent a great deal of time writing 'thesis' note sets, so what nearly every angle i thought about before i got into that exam.
i had so many sets of notes for different purposes, i had a thesis set, a fact set, an essay set, a set that i just couldnt get into my head, ect ect
so i wouldn't worry about the size and length, just make sure that its an amount that you can manage and learn over time
its important to look through your notes and review them to make sure that by the end of the year, you will still be able to understand what you meant! (alot of people including my self had this problem)
also try to be realistic about how much you will cover in an exam
its all very well to have 100 pages of world war one "facts", but think to yourself
'how much can i realistically pack into a 25 minute response?', 'can i really learn all this?' and try to cut out facts accordingly
i tried to find facts that i could use in a range of questions and only learn them and that worked for me too towards the end
its also been suggested that you only need to learn 5 - 10 actual 'facts' per dot point in world war one, so you could always work from that angle as a rule of thumb.
all the best x