Replacing the flexible lines is a walk in the park. What is at issue here is corrosion leading to bursting of the hard lines (rigid tubing) of the hydraulic system. In my entire life (71 years) I've never had a brake line fail until recently. I understand that other tubing - fuel lines, transmission cooler lines, etc. is also corroding prematurely on these trucks.
My personal vehicle is a 2005 GMC Sierra 1500 Crew Cab Short Bed 4x4. I bought it new. Since I'm retired and like staying at home, I don't drive it much, particularly in the winter here in NJ. Last week my odometer reached 42,000 miles. The day before Halloween I had to go out to buy treats for the kids. On returning home, while maneuvering my Sierra to park it in my driveway, my brake pedal went soft and oozed floorward. At the same time, I noticed something like steam coming out from under the hood. On investigation I found that a rusted brake line clipped to the top of the chassis had sprung a leak, and was spraying brake fluid onto the hot exhaust manifold.
I understand that these lines are not available as replacement parts from GM. They must be fabricated by the dealership mechanics. The hours required to do this not only make the job very expensive but also introduces the potential for TIF (Technician Induced Failure).
Steel tubing fittings threaded into alloy components can be a real challenge to remove without ruining the component. And the dealer will use the same steel tubing as the original, meaning that you can look forward to it rusting through again.
A complete set of brake tubing in stainless steel can be purchased for about $330. But the labor necessary to install even these pre-bent tubes will still be considerable.
To say that I am disappointed with General Motors would be an understatement.