It is located on the throttle body:
Fig. Air passage breakdown, mounting screws (4) IAC valve (3) O-ring seal (2) on 2000-02 4.8L, 5.3L, 6.0L engines
Fig. Throttle (TP) and air intake control (IAC) harness connector
No, you can remove the IAC valve without removing the throttle body. the one diagram just shows it with throttle body removed for clarity.
remove the retaining screw and connector(2 red arrows pointing at them), and then remove the iac valve
I believe yours has the electronic throttle body then, which means that the IAC valve is integrated into the throttle body and not servicable separately.
below is electronic throttle body. If this is yours, then the IAC valve isnt servicable:
If you are having idle problems, there is a TSB on this issue that states to clean the throttle body and then the PCM is recalibrated-this can only be done at a gm dealership with their software and scan tool:
#04-06-04-040: Idle Instability, Low or Rough Idle with Electronic Throttle Control (Clean Throttle Body) - (Jun 14, 2004)
Some owners may comment on an idle instability, low idle speed or rough idle.
Condition may be caused by deposits in the throttle body bore.
Clean throttle body bore and throttle valve plate of carbon using a shop rag and an appropriate cleaner. Refer to Engine Controls Repair Procedures - Throttle Body Cleaning Procedure. This procedure may be performed at any mileage necessary. Check to determine if the PCM calibration has been previously updated to one that includes the update for throttle body coking. For 2003 model year vehicles, look in the operating system portion of the calibration. For 2000-2002 model year vehicles, look in the engine portion of the calibration. If not, then update the PCM calibration to the latest calibration.
Below is a repost of my last post on idle concerns for this engine. I would recommend cleaning the throttle body and then having a gm dealership do the PCM recalibration. This should take care of your problem