Idleing

This could be several things, really need to see the scan tool data of the engine values while the engine is running, you could have a vacuum leak, a defective idle control motor, I have even seen arcing ignition wires cause a surging idle. here are some shops: https://repairpal.com/chevrolet-repair-in-rustburg-virginia

I'd suspect that the throttle body is fouled with carbon. You can clean it with a rag and 'throttle body cleaner' or Chemtool, etc. try that. I'm assuming everything else is OK. PS: Dandd's answer is better than mine, so listen to him too.