He won't serve a year for selling an ounce of weed... that would be highly unlikely.
Get a lawyer, he'll get probation... probably with the condition of a substance abuse program. Look... they always tell you your getting the worst to scare you into turning a rat.
Turning the rat like the guy did to him is way harsher of a scenario then getting a lawyer and fighting it and taking the probabtion. I know a kid that was faced with that choice and in the end talked to others that turned, and realized they make your life hell... it never ends, don't cooperate, piss them off the threat of jail comes back.
You're better off lawyering up and taking the probation and moving on with your life. The rat things never ends, and makes your life hard.