Can someone tell me what a cruise control actuator, amplifier, and coder does. Do either of these items require resetting?

I'm still having problems relating to a CD Head installation. Cruise control worked fine before install, but now the Saab dealer here in Nashville is saying their not responsible.

The amp is the control unit. The coding plug is the add on chip that tells the amp what car it is in.
The actuator is the physical arm that actuates the throttle.

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Benzmac:
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
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Benzmac,

How is it possibly connected to the Radio? What could they have done while installing a new head. The MBZ dealer here wants $130 just to diag.. Does that sound right?