1993 GMC Suburban Headunit

Hi Got a 1993 GMC Suburban (K1500) with the stock 6 speaker system.   Going to swap the headunit out first, but i'm looking for tips. Its been nothing but rain here so i havent had a good day to pull it all apart, but thusfar i can tell theres atleast 3(?) pieces to the stock stereo. From what i can see, the controller at the dash above the climate controls, the EQ/tape deck thingie in the center of the dash, and some kind of brain/main unit SOMEWHERE in the dash. Can anyone confirm this? tell me the most efficient way to get to the harness so i can plug into it. And anything to watch out for while doing this? Thanks. Also: where does the 6 channel system come into play? as far as i know theres 4 output channels on most headunits, are they running a low impedance on the 4 rear speakers? separate amp? Is there a known strategy for this particular situation? Thanks alot, -Jim

Thanks for that, Seems simple enough.   I will get to it today with any luck.    Hopefully someone can chime in on the 6 speaker system, or i can just tear it apart and see what happens. Thanks -Jim