1) Separate the handle from the chamber by unscrewing. Holding the chamber head securely in a vice, upside down, is a good idea.
2) Once separated, you’ll see the gas nozzle (gold piece) and O ring. At one point in time these were threaded, now they are just positioned inside. They are easily removed.
3) Replace with a new gas nozzle and O ring and screw the handle and chamber back together. It’s important to firmly push the gas nozzle into place.