The inside door handles are prone to breaking.Google+
Car Problem Reports
GMC Sierra 1500 Inside Door Handles May Break
GMC Sierra 1500 Problem
Average Mileage: 117,333 mi (89,000 mi - 138,000 mi)
Visitor, 1999 GMC Sierra 1500, 138,000 mi
Inside door handle for right rear door broke.
Visitor, 2000 GMC Sierra 1500, 89,000 mi
This is a well known manufacturer flaw. Although GM decided to sweep it under the rug. Have had to replace the drivers side interior handle once a year for 5 consecutive years. Also had to change out the exterior door handle, and lock-set (tumbler) once. The fun really start when both the outside and interior handles decide to break at the same time.. then you can open your door at all without calling a locksmith with a "slim-jim" ( expect to pay $100.00 for that, on top of new handle. Now my drivers side door, which is hardly been used is now malfunctioning, causing me to have to crawl out the though the backseat.. This is just plane laziness on the behalf of GMC engineering "Way to go UAW!!"