1- You don't
need any LEDs, you could just use a DPDT instead. However, if you want an indication, its nice to have a visual for both conditions, but perfectly acceptable to just use one of them.
2- If you use a superbright LED, the CLR (current limiting resistor) can be 47K (or larger) and still give a very bright indicator. Using Ohm's Law and a 9V battery, you would be drawing about 191 micro amps, which will last a very long time.
How long? According to the Duracell Copper Top data sheet, a 9V alkaline battery has about 580mAH capacity. Even if you only use half of that capacity before the voltage falls below usable levels, that is 290mAH. Divided by the current draw (.191mA) gives about 1500 hours continuous operation, or about 63 days. Unplug the guitar cable when you're through playing, and it can last years.
3- Ground: sleeve of the guitar input jack, and 0V from your 9V power source.
4- CRL = my dyslexia on full public display

This should be R
CL (Resistor Current Limiting) or CLR (Current Limiting Resistor). You can use whatever value that gives enough light on stage. I like blue and green 3mm waterclear LEDs with 47K.