I undertook this endeavor because I broke it by disassembling incorrectly causing the switch wires to twist off of the light engine, in for an inch, in for the mile. So to save anyone else from reinventing the wheel, I posted the procedure as follows:
I have opened my Spark ST 360 CW and want to share this unique experience with you without photos. I did not change the led, only disassembled.
There is talk about it being upgradeable and while true, it is a tedious task with this headlamp and it can be successful if you understand what I am going to explain.
First, the end opposite the battery cap is a threaded tube requiring force to loosen. Upon removal, you will see inside the body a ring with a red wire soldered to it, that will need to be unsoldered and the ring removed and set aside to be resoldered at assemble time.
Next is the finicky part, removing the switch boot and chrome beveled ring holding it, so that access is gained to the switch and the wires can be unsoldered and retracted through the switch pcb pass-through holes effectively removing the switch and stuffing the two wires into the body of the light and then removing the bezel, lens, o-ring, and reflector and using needlenose pliers, unscrew the light engine using the slots.
A note on removing the chrome ring holding the switch boot: I tore my cover gaining access to the chrome ring, having to insert a small flatblade screwdriver assisted by turning with pliers to eject the ring from the body and then superglued the tear back together.
Assembly: I unsoldered the switch leads from the light engine adding my own 3 inch long leads to facilitate putting this back together, here's how. With the longer leads soldered on light engine, align the light engine as you are going to mount it back into the body and pass the two longer switch wires through the switch hole and then start threading the LE in carefully. stopping each revolution to pull the switch wires straight and untwist them until the LE is bottomed out. Then snip the wires, leaving about 3/16th outside the switch hole to allow you to pass them back through the switch pcb and resolder them and put the switch boot back on and press the chrome ring back down.
Now fish the red wire through it's hole and place the ring back in and solder it and thread the tube back on, add battery and cap, install reflector, o-ring, lens, and bezel and there you go