The Idle Air Control Valve will be located on the throttle body somewhere close to the throttle linkage depending on the year and engine (you failed to give the details on your truck).
It is very easy. On my truck, 93, 2wd, 5sp, 4.9L, I only had to disconnect the electrical connector, remove 2 bolts, install new gasket and IAC then reconnect the electrical connector.
You can check the electric part of the valve by ohming it out with a meter. It should read between 7 and 13 ohms. You can also try cleaning the inside of the valve with carb cleaner. You will need to take the eletric part (metal cylider with the elec. conn.) off of the valve (two phillips-head machine screws) so the cleaner doesn't get in it. Be sure to put the o-ring back on before you reassemble the two.
Remember to clear the codes if you replace the IAC with a new one.
Hope this helps
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