Honestly tutoring isn't necessary.
Tutoring can certainly help but in the end it's all down to how much effort YOU put in.
My advice would be to go through and learn a bit of the content before classes start next year.
Don't go through absolutely everything. I wouldn't recommend it. It's unnecessary. You'll probably forget most of it because you're overloading your brain with so much information that it won't be able to remember everything. Save yourself unnecessary stress.
Just go through the first couple of chapters or so for Unit 3 and make notes along the way. The goal is to make sure you always stay ahead of the class so every class you pretty much aren't learning anything new, but just further consolidating your knowledge each time. Also learn how to answer questions! Do a lot of practice questions.