If you look under the passenger side dash, there is a plastic pan with 4-5 screws holding it up. Remove that and you should see the air box for the heater/AC. There will be a small access panel about halfway between the door and center console with one screw holding it on. The back of the panel has a tab to hold it up. Remove the screw and drop the panel. You should see the bottom of the first filter. NOTE...there are two filters in there, one on top of the other. Pull the first and hopefully the second will drop behind it. If not you may have to get a long something and fish it out. Repeat backwards to close it up. This is thru "02.
Between the dog, the hunting lease and the general blowing $hit around town, I replace mine every year. You can get the "plain jane" filters or the carbon panel filters if you have a lot of environmentals.
'02 Silverado Z-71, STS Turbo @ 10psi, TRT Custom FMIC, Comp 222/218/115 cam, Patriot Gold Dual Springs, Hardened Push Rods, 60# injectors, 160 Thermo, FAL E-Fans, Nelson Harness, Yank 2600, Built Rock On VacMod 60E Transmission,Walbro 255 fuel pump, ASP Underdrive pulleys, Gibson Shorty Headers all polished up with a Nelson Street Tune