[Mad Scientist Jr[_2_]]

I have an old PDA that I would like to modify (if possible) by taking
out the built in condenser mic and replacing it with a 1/8" or 1/4"
jack that I can plug another device into. Mainly I want to plug a
standard stereo headphone output (from iPod/cellphone/walkman/etc)
although it would be cool to be able to connect a line-level out from
a mixer, or directly plug a guitar in. The latter ones would probably
require a different circuit so for simplicity I'll just stick to the
first scenario (headphones out). Assuming I successfully can de-solder
and remove the condenser mic from my PDA and have two leads (which
went to the mic) free to solder my new input to, what kind of circuit
do I need to place between the new jack and the leads, so the input
works? The PDA must have some kind of preamp built in to drive the
condenser mic, so I am thinking maybe some kind of resistor or volume
control to "step down" the signal strength before it goes into the
PDA's preamp? I suspect the audio fidelity won't be the greatest, but
as long as it's passable I would like to try. Any info would be most
appreciated... thanks.