Hey!
I just began electronics with a friend but we kinda get crazy about it.
So we built this project and we were thinking about putting it into a guitar directly

Don't worry, we have an old cheap guitar we can try this on (and we won't do it on the good ones)!
So I guess we'll just stick to this wiring :

but with a few questions :
1/ I don't think we will put a LED, does it matter if we just remove it (with the resistor) and leave the wiring the same or do we have to change something?
2/ The output jack of the guitar is mono, do we have to replace it with a stereo for the ground?
3/ Do you see any other problem we wouldn't have thought of?
I was thinking of putting everything below the pickguard and just have holes for the pot and the switch and putting the 9v battery on the back (with a battery holder similar to those you can find on basses) with only small holes to have the wires connect to the circuit.