I do not own any Serge modules but have done module repairs, system restoration, and complete system rebuilds. There is a lot of good information on Serge at www.serge.synth.net/.
Serge 3 Boat System Rebuild (new panels)
Serge 1 Boat System Rebuild (dark panel)
Serge 3 Boat System Restoration
Serge WAD (Wilson Analog Delay) (FRAC format)
LEDs were mounted on a small PCB that soldered to a banana jack for mounting. The LEDs solder into one of the sets of two holes at the bottom depending on the spacing from the banana jack.