[Huck]

Cleaning the throttle body is simple--just remove the plastic that connects from the air cleaner to the metal throttle body unit. The throttle body has a metal flap that opens and closes to allow air in. This flap tends to stick as the walls of the thing build up with oil crud over time. My Tahoe needed cleaning with just 35K miles!! My 2000 silverado with 156K miles gets it cleaned once a year. Spray the throttle body cleaner in there, wipe it out with a clean rag, then check for the likage to work smooth. That should do it. Takes about 10 minutes. Run a bottle of "Techtron" through your gas tank once a year to help keep your injectors clean will also help.
If your truck has the tow/haul feature, expect that to stop working around 50-70K miles. the fine wires from the shifter stalk will break inside the steering column--simple fix as well. You can also expect the anti-lock brakes to give you trouble--recall to clean the rust off the sensor mount.
And your Vortec motor will start to give you start up noise like valves tapping which is common to all of them. This will make you nervous but it normally stops within 10-15 seconds after a cold start. Mine has been doing that forever with no noticeable problems.