If it's leaking around the reg adjustment screw it is good news (easy fix). If the leak comes from the tiny hole facing the bottle/cylinder it's a PIA. As Keyman noted - two small o-rings on that reg screw may need replacing. That reg screw can back all the way out; there is no catch. You'll see the two o-rings on the tiny brass reg piece, and you'll pretty much need to destroy them to get them off, so make sure you have replacements before you go for it. Oh, and make sure you're degassed.