Powertrain Control Module-Body Control Module- and about another 20(around a hundred more for newer vehicles) modules located throughout the car that talk to each other over the Class 2 Data bus.
The cruise control(stalk) is probably tied directly into the BCM, and the BCM talks directly to the PCM. Without the Factory Service Manual(FSM) we won't know the specifics of the system.
And your pretty much SOL without a scantool AND the book.
Did you know, the typical cruise control system will be disabled when the PCM is detecting a misfire? When was the last tune up?
1997 Pontiac Bonneville SEi-SCRAPYARD
2000 Chevrolet Blazer LT 4X4 4.3L
2002 Chevrolet *-10 LS Ext Cab 4X4 5.7 V8