Ok, I have 2 questions-

1. Ive seen some switches at radioshack that have light up functions. Would I be able to use these as a killswitch? would the lights work?

2. I also seen LED lights. How would you go about adding these to mod your guitar?
The switch would work as a killswitch, but I believe it would need an external power supply. You can wire as many LED's as you want like this..

These go to eleven...
Erm are you talking about a pushbutton with an internal light inside it? If you are, and you wired it as a killswitch to the guitar, wouldn't the power from the guitar, when its connected to an amp, be powering it?