GW isn't going to affect your sex hormones, as far as I'm aware. There is no PCT.
I've never run it, but from what I've read, it should be run anywhere from 10-20mg per day, for cycles lasting a couple months. I'd probably take at least a month off afterward before using it again.
As far as testosterone goes though, the best way to prevent unwanted sides and after-effects is to read a lot. Educate yourself on what needs to be done during and after a cycle. No one here wants to spoon feed you. I do disagree with what paulaner said regarding your age. I don't think there's a big difference between starting at 20 or 30, IF YOU KNOW WHAT YOU'RE DOING. It's clear that you don't yet.
Here is what I consider to be relevant as to whether or not you should run a steroid cycle. You should be able to clearly answer the question "why are you doing it"? How good are you at crossfit? Are you good enough to make a run at being a high level national competitor? Good enough to make some money at the sport? Or perhaps right on the verge of being good enough and need an extra edge? Or do you just want to compete with the guys at your gym? Or in your city? After you answer these questions, you have to ask yourself if the risks are worth the reward, FOR YOU. Do you want to risk testicular shut down and a liftetime of TRT to beat a dozen guys at your gym? Probably not. Is the risk worthwhile if you might win a million dollars in the Crossfit Games? Probably. I'd do it.
These questions become easier to answer as you get older and your priorities come into focus. That's why most people will tell you that if you have doubts, wait. You'll learn what's important to you and what's less important. I waited until I was married, had a child, and knew I didn't want to have any more children, before I started. I'm 31 years old. And I have specific powerlifting goals I want to achieve.