Any tips on gaining access to the inside? I need to cut around 5 inches of cable off and re attach them.
Slow and steady. Thinking through, there's nothing particularly shocking about getting in there.
Unscrew to loosen the gland (leaving the base installed in the battery can).
I didn't have a pin spanner so I made one out of a piece of wood and two nails to open in the battery compartment. Unscrewed easily and reveals the board.
Used a combination of pushing the wire simultaneously with pulling on the board to dislodge it. I'd be worried about damage otherwise. Didn't need a heat gun, just firm consistent force. Perhaps consider a heatgun internally (watch the gland).
Soldering the leads be aware there isn't much room in there, copy the original lengths and angles and how much wire is stripped etc.
As you dig into it feel few to shoot me any questions as you go. I don't have much focused attention left these days for thoughtful posts but do check the forum very regularly and can shoot quick replies. (Just because I've done the repair before, not an expert on dive lights)
Good luck!
Cameron