+1 to the Food Solutions textbook. It's the one my school uses and it's great.
You can easily pick it up. The only thing is, there's quite a bit of repetition of theory, so while most of the class will be like "psh, key foods? got this" (which comprises 2 chapters of the textbook - the other repeated chapter is food safety, I think that's all?) you might be like
"yep gotta go over this in my own time to catch up".
In addition, hmm... Year 11, you get taught "X is a letter with two strokes that comprises the makeup of it". Whereas, in Year 12, it'd be like "X is a letter with two strokes that comprises the makeup of it, also [paragraph of history] [paragraph of changes in the use of x] [paragraph of. i dunno. modern applications of x in design]". (wow that was a terrible analogy I am so sorry but basically I'm just trying to say a lot of 3+4 theory is just expanding on 1+2 theory, except for the repeated stuff in the above paragraph).
BASICALLY YOU WILL BE TOTALLY FINE. ♥