Yes it is possibile to do. However, it's going to require tapping into a few wires.

It should be the same for the L series, VUE, and ION, as they all use the same stereo. This is from the L series service manual, but I recommend going to http://www.saturnfans.com/forums/ and asking the question there. Lots of people who work for Saturn / GM, and/or have access to information should be able to find exactly. what you are looking for.

Based on the 2000L service manual..

left front gray and tan
left rear yellow and brown
right front dk green and lt green
right rear lt blue and dark blue

orange for clock
yellow ign
gray dimmer
brown park lamp input

subwoofer dk blue/white and lt green/black