It's fairly easy to do if you have the knowledge and the tools. You will need Phillips Screw Driver, fine needle nose pliers, and a soldering iron for tools. Solder wire and thermal paste for supplies.
Also important would be diagnosing the cause of the failure. XML/XML2 emitters don't generally fail in a flashlight unless something is causing them to get too much voltage or letting them get too hot. Since the cells are parallel in that light, it is probably a heat issue. Something that should be obvious when you replace the emitter. It could be just a bad connection though. Another thing to look for as you work your way into the light.
High level procedure to replace an emitter in that light:
Remove button cover with fine needle nose pliers. There are indents to engage the cover. Pull out button circuit board enough to allow getting a tool through that can be used to push the driver out.
Feel around for an area that doesn't seem to have any components. Push out driver. They can be very stubborn in some SRK's. May need to uses heat (not so much you damage driver) if glued.
Once driver is out. Use a Philips screw driver to remove screw holding down the reflector (one screw in center if you have a 3 emitter version).
Unscrew bezel and remove lens and reflector. Be very careful handling the reflector. The finish is extremely delicate.
Look at wires to emitters to see if their is a connection issue. If you have a DMM, you can do this:
Unsolder one of the LED leads for the emitter that doesn't light.
Set your DMM to the Diode Testing position and place the Red probe on a Positive Pad of the LED Star and the Black Probe on a Negative Pad.
If the emitter works it will light up.
If not, you likely need to replace the emitter. Verify the meter works by testing a good emitter.
If the emitter is bad, procure a new one. This is a good time to procure one of a warmer tint if you want that. If you plan on souping up the light for more output, this is a good time to replace all 3 (assuming 3) with emitters on copper stars. Test them to make sure they work before installing.
Remove the bad star and clean the pill surface that it sat on. Solder the leads to the new star.
Put a little solder paste under the new star and put in position. Good time to test if it all works before the next step.
Reassemble your light and test.
Enjoy your repaired/enhanced light.
At this point I would snap a couple pictures and post them here o determine the next best step to take. Since you have plumbing trade skills, More steps were added above.
I am a plumber by trade so solder on a daily basis but on a bigger, hotter scale I guess. I’m a complete novice when it comes to the world of torch building/modding!
I do own soldering irons so will follow your detailed instructions & hopefully won’t mess it up-lol
Expect another post soon titled “help, my skyray is in bits” hehe
With plumbing skills you will cotton to much of flashlight modding quite well. Just post questions and if you can pictures when you hit snags. May folks here love to help out.