NSBU Switch
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, 2003 Chevrolet Cab & Chassis Silverado, and 2002 GMC Sierra. However, it is still accessible from the selected car via links, so may be relevant.
If equipped with NSBU switch, use a wrench to keep selector lever from moving while removing lever-to-shaft retaining nut. Remove selector lever and 2 NSBU switch retaining bolts. Remove switch from main housing and selector shaft. See Figure.