installing L.E.D. in distortion stompbox?

[ginger]

I have a pair of cheap, very simple MXR distortion & compression stompboxes. I'd really like to install an L.E.D. that lights up when the effect is on. I'm fairly new to tinkering with wiring but have recently done several projects with success (notably the guitar shielding project that brings everyone here). Basically, I haven't gotten the hang of working out new designs on my own but I'm good at following directions.

Any help working this one out? It seems like it should be a simple mod, except for the annoying drilling through the casing to install the L.E.D. I need to know where in the circuit to insert the L.E.D. and how it will power itself.

Thanks a lot for any help getting me started!