OK.
Personally, what I found was needed from 1/2 chemistry in 3/4:
Organic nomenclature
Really simple acid-base stuff
Redox reactions
Gases, concentrations and stoichiometry
Maybe solubility? Not too important in 3/4
As you can see, there's not too much that you DO need to know from 1/2
Anyway, what is the best way to learn the different analysis techniques? For example, mass spec. Should I aim to develop a deep understanding of the process, or is that a waste of time?
Personally, the way I learnt them was that I kept reading them until I could explain them to myself and that it made sense. A deep understanding isn't really needed; perhaps just learn what's in the textbook. I've found that's more than enough.
Look at that, I might actually be able to help here next year. Unless of course nliu is still around, I can't compete with that.
Hey, with that attitude, you really won't be able to help

Should I spend the summer reading over area of study one of unit 3?? I'm probably going to spend a bit of time going over 1/2 content relevant to 3/4 chem.
What I did in the holidays was that I read through the entire textbook and noted what I found easy and what wasn't so easy. For me, generally it was ok, aside from fractional distillation (like, the exact mechanisms at play, and guess what happened to this part of the course?), analytical techniques and biomolecules (I just hated biology in year 10). I did enough reading to have an idea of what they were, but maybe not a particularly in-depth knowledge. By the time class time came to look over those things, I had seen them before, I had thought about them, and remembering that stuff became easy.