[Dr.Fiero]

If the idle EVER goes up/down, you at least know that the ECM is hooked into the right spot, and has the ability to control the IAC motor.

Chance are that the IAC motor is just sticky, so you're getting the random action.

It's located on the drivers side of the throttle body, right below the TPS. Big square 4 pin connector.

 

[Dr.Fiero]

It's no worse than changing a spark plug - ok, a BIG spark plug.

Just gently pull back the clip and remove the plug.
Then use a (24mm????) wrench or a 12" adjustable and unscrew it.
Check the new one's extended length (of the pintle) and make sure it's not poking out more than the old one. Screw it back in, and give a snug down (don't kill it). Hook back up, go for a drive. it should straighten itself out in the first 10 min's or so depending on the temperature.

 

[Dr.Fiero]

Good chance! It's just a little itty bitty stepper motor, and the water could have confused it. There's no feedback to the ECM from it, but still.... water and electrons rarely play well together.