Most of that stuff would have been removed prior to laying them up. So much of the cost of bringing those ships back to life would be re-installing that weaponry/sensors on their mounts and testing. Not sure what state the engineering plants would be in.
They are LM2500 Gas turbines. If absolutely needed you just drop a new one down the the stack pretty much. Watched one of our Des-squadron mates replace one in 3 days. across the pier from us.