Brake Disc Caliper problems of the 2003 GMC Sierra 3500

I recently had a brake failure on my 2003 GMC Sierra 3500 series truck. I was driving when my brakes gave out. The pedal went to the floor and I was barely able to stop before striking a parked car. I took it to the dealer and was told that my brake lines and calipers are corroded and in need of replacement for a $4200. I had the brakes replaced last February and put less than 1000 miles before this incident. The rear brake pads which were replaced then needed to be replaced because of corrosion issues. I have had to replace the brakes on this truck 4 times since I purchased it each time because of corrosion issues. I have been told by gm that I do not drive the truck enough. I am afraid to drive it for two reasons 1. It might not stop when I need it to and 2. Everytime I drive it ends up costing me more money. The transmission lines were replaced last summer for the same issue. This truck has cost me over $20,000 in repairs since 2005 not including maintenance issues. When I contacted gm customer service they were absolutely no help. I was told I do not drive it enough and the fact that the truck is older it is a part of life. They would not even acknowledge that they have a problem. I was told that the NHTSA is conducting an investigation into this matter with gm. If you need any help please call me I would gladly help in this matter.