help with A/B(C) switching project

[benl560]

ok, so im pretty new to all this so bear with me.  Id like to build a switching box to switch between 3 input sources (guitar, kaossilator, weird sound generator). the guitar and the weird sound generator use 1/4 mono and the kaossilator is stereo rcas.  i would like to have a volume control and led on two of the sources, but i dont think i would need it for the guitar.

now, my question is, to have a volume control, would i need to have what would essentially be two volume boost circuits or could it be as simple as sticking a pot inline with each?
also, im not quite sure how i could route a mono and stereo out to an amp.

any help would be appreciated...