Hi Geoo!
Please don't feel scared! It is really possible to do well in Methods, even if you didn't do the best in 1/2. Depending on your teacher, they might go through some topics from scratch. My 3/4 methods teacher went through everything in detail, even teaching us how to graph basic functions from scratch.
Unit 3/4 builds on topics learnt in 1/2, with a few added ones. Theres no much point going through the entire 1/2 course. Some topics, such as kinematics, is taught extensively in 1/2, but barely touched upon in units 3/4. Just to save time, you could go through the Unit 1/2 study design, and compare it with the 3/4 and learn the topics that over lap (if that makes sense.)
If you have access to them, it might be worthwhile skimming through the SACs set in Unit1/2. Learning CAS functions will also be a lifesaver.
Some topics that is worth going over during the break is: (You can go through these into 1/2 standard, 3/4 standard should be taugh during class, but wont be that much harder.
1. Sketching basic functions (quadratics, hyperbolas, truncus, square root graphs, quartics, etc)
2. Transformations/Reflections (An important one! It will help you so much if you can learn these well)
3. Properties of th Derivative function, how to use it and what is signifies
4. Basic sine, cos, and tan graphs, and solutions of these
The biggest tip I can give is don't stress. Work through everything slowly, and target your weak spots
I hope this helps!
Good luck!