2000 GMC C2500 rough idle

This could be a few things, but first I must tell you about the plugs and wires you used. They simply stink. Bosch spark plugs should be taken off the market. I'm not sure about the auto lite wires either. If this problem started after you changed these items, I would at least change the plugs. The wires, being that I'm not sure about them, I would change too. A/C Delco plugs should always be used in these motors. Be sure the gap is set to spec. A/C Delco wires are expensive but they are properly designed for these high power ignition systems.
Is the check engine light on? Normaly, when any sensor is malfunctioning, the check engine light will come on. Do not go changing any sensors until you test them and determine that they are bad. Autozone or a place like that can and will test almost any sensor on your truck. Usually you can take it off and take it to them.
The sensor your friend speaks about just happens to be a sensor that, I believe, cannot be tested at autozone. It's the IAT (idle air temperature) sensor. This sensor adjusts the idle according to the air temperature by using a resistor that changes resistance according to the temperature. WOW sounds complex? It is just that, but it is easy to change. The coolant temperature sensor works the same way too.