Yes it's possible, but it's expensive, and hard to find a vet that will do it because it's considered cruel by many people. (Which doesn't make sense to me if the alternative is the stewpot - I'd choose to be mute over being dead!) It also has a high failure rate. The roo will NOT in permanent pain after the procedure.
As for doing it yourself, I've looked up the specific ways of doing it - PM me if you want references to the scientific literature - you can go to the local university and copy the articles. It is not recommended to do it yourself because it requires some knowledge of anatomy and sometimes anesthetic (depending on the technique). Also, amateurs have a higher chance of killing the bird in the process.
I looked up all this stuff because I had a cockerel and would've tried decrowing him if I hadn't found a home for him. If you can't have him crowing and you don't need fertile eggs, try to give him away first. If you need him, try keeping him in a dark place for the night so you can control when he gets light in the morning. If you can't do that, then you might look into decrowing, but it's something that should be a last resort.