Is it possible to solder LEDs to a Nightfox with the switches soldered on?

edit

(edited your question a bit to make it more clear)

Yeah, you'll have no issues soldering LEDs onto your NightFox. The general process for soldering through-hole LEDs on switches is

1. Solder switches to PCB
2. Insert LED into switch (make sure the long leg matches the square hole)
3. Solder the LED in place
4. Test all the LEDs
5. Clip the long tails from each of the LEDs (clip at the end to make sure all the LEDs are working and soldered correctly, but make sure they aren't touching when testing or you'll have an interesting light show).

Hope that helps.