1997 Cadillac SLS idle control system

1997 Cadillac SLS V8 Front Wheel Drive Automatic 00k miles

I was riding with my cruise engaged. A message appeared on my display-- Service Idle Control System-- My cruise control disengaged, the speedometer went to zero and the transmission quit pulling. I went to neutral and back to drive and was able to get home. Now it works ok for a while and it will do it again and the speedometer goes up and down to the speed you are going. Sometimes the transmission will not change gears unless you hit the gas pedal. The cruise and speedometer will not work. Does the idle control system control this and is it something I can buy and install myself?