Reddit reviews Fundamentals of Geometric Dimensioning and Tolerancing

For starters there's a couple of good books on amazon...This is the one that I use.
Fundamentals of Geometric Dimensioning and Tolerancing by Alex Krulikowski

PM me if you want to talk more.

Sounds like you need to hit the internet hard or pickup some books on print reading because man, if you're taking CNC classes and can't read a print, you're in over your head. My trade school required manual machining and print reading before being allowed to progress into programming and CNC machining.

Print reading is fundamental and if you can't read a print well, you can't program and you can't decide what strategies to apply to your process. You'll end up an operator without it.

Theres also several different ways tolerance prints, GD&T seems to what everyone is moving to. That being said, about half the prints I get are ASME and the others are GD&T.

You'll have to find out what system is going to be used in your classes and go from there to decide exactly what you need to learn for your education. For GD&T I used: http://amzn.to/2tiWi8T and it was okay but not great. ASME was included in another textbook I had at the time.

Good luck man, print reading is absolutely critical to being successful in this trade and most shops won't look at you twice if you can't read a print.

Edit: Forgot to add to brush up on your trigonometry.

https://www.amazon.com/Fundamentals-Geometric-Dimensioning-Tolerancing-Krulikowski/dp/1111129827/ref=pd_lpo_sbs_14_t_0?_encoding=UTF8&psc=1&refRID=J79KBEFH0WKF6KDZ2B0X

Its a steep price but its what I used in my GD&T course.

If you want something like a course with everything broken into pieces and with review questions after each lesson its not bad.