monitor a guitar signal strength, then output a DC level?

[HankMcSpank]

I'm at an early exploratory stage, where I'm looking for some circuit or other (not sure if it'll be PIC based or not yet!), to do the following....

Feed a guitar signal as an input to a a PIC input pin.

Have this incoming signal level monitored...then output a DC level on an output pin that's inversely proportional to the incoming signal. Therefore if the overall incoming signal is too high, drop the DC level on the output pin. If the incoming signal is too low, raise the DC level on the output pin

This DC level output will be fed to an audio power amp chip that has a DC pin dedicated to volume control.

So in essence, it's an AGC circuit...but utilising a PIC to do this (yes, I know there are probably specialised ICs that already do this, but I have a unique need & need to control the charactersistic of the circuit)

Is this do-able?

If so...a lot of code? (I'm new...having just done a small amount of programming...though I did get my first PIC project working!)

Anyone got a link to something I could rejig?

Any comments to get me started most welcome!