The CCM is buried behind the bezel that frames the DIC/A-C & radio. If I remember right the stack of stuff has to come out, and then the DREM comes out ( discon battery & wait 15 mins for SIR system to loose stored voltage ) and then it's under the DREM....I think? Or behind more to the firewall? Sorry, senility stinks!
Console has to come out. Remove the shift knob & rev lock out ring by prying up pattern plate & pull out the "T" wedge & unscrew knob. Locate all the 10 mm small bolts for console under lid & ashtray. Then remove the A/C register above DIC. You'll see the screws holding the bezel in place, BUT be aware of the two spring clips about the mid point of bezel. I snaked my fingers to both sides of each clip and pulled evenly on the left & right sides of the bezel to get them out. Careful or the bezel could break. Then discon the power key harness & then the DIC & A/C & Radio can be removed. That's the short version of the procedure.
There is one other possibility that is just as distasteful : the ignition key cylinder has a wire that is prone to breaking off the cylinder. Somehow I'm not sure this is a worthwhile suggestion to run down until you exhaust all the other possible causes for no start.
You are absolutely sure that all the battery connections & grounds are 100%?
I'm not trying to be a wise guy. The battery was charged & load tested? Hydrometer tested? & Last a volt reading? The CCM maybe NLA from GM. A new one needs to be reprogrammed or loaded with your CCM's info or the car is dead. I think if you call Gordon Kilbrew or Marc Haibeck they can suggest where to get your CCM rebuilt....I think?
Tom