Your 2006 Tahoe has disc brakes on the front and rear- that is the only way they were built. So, they do not need to be adjusted like drum brakes, they 'self adjust' as soon as you pushed the pedal down the first few times you press the brake pedal, the caliper piston pushes out until it contacts the brake pads, which in turn contacts the rotor- viola! adjusted! Some people have always complained about the 'spongy' pedal on those C/K trucks since they were redesigned in 2000. GM tried to make a few changes during those years until 2007, when the truck was redesigned again. The newer Tahoe/Yukon (2007-2012) has a much firmer pedal feel. If you have a hydraulic brake booster, a spongy pedal can be considered normal (ask a qualified gm technician to check pedal feel). A hydraulic brake booster will have hoses running to it from the power steering pump. If you feel like your pedal is still too spongy, the first thing to do is check for a leak. Obvious checks at the calipers, hoses & lines should be easily done, however, most people don't check behind the master cylinder. A leak behind the master cylinder won't always leak on the outside of the brake booster. If you have a vacuum brake booster, you will have to take the 2 nuts off (15mm) and slide the master cylinder forward, stick something long and thin into the hole (like a screwdriver), aiming towards the bottom of inside the brake booster (use like a dipstick). If fluid is on the makeshift dipstick, your master cylinder is leaking. Normally, you do not have to bleed your brakes if just replacing pads and rotors, definitely necessary if you opened the hydraulic system at any point (cracked open a bleeder screw or line fitting). Brake lining material has no affect on pedal feel. New brake pads, no matter what they are made of, will need to seat (break in) to the new rotors. Until they do, you may have brake fade when coming to a stop the first few times braking. This will go away in a short amount of time depending on how aggressive you brake. Ideally, you want to brake with medium pressure on pedal at lower speeds (25-45 mph). Maintain constant pressure from moment you start to brake until you come to a complete stop. A few times doing this, and the pads will seat. Lastly, brake fluid does not EVER need to be changed unless it is contaminiated. It is true that air (moisture) can affect the boiling point of brake fluid, but most people don't leave the system open for significant amounts of time. Brake systems are SEALED and air doesn't just seep in. The discoloration of the fluid is NOT an indicator of the condition of the fluid. Brake fluid changes color due to heat, not moisture. Shops recommend changing brake fluid based on color as a way to make money (same with power steering fluid). Certainly, it doesn't hurt to do this as preventive maintenance, new fluid/oil in anything always works to its highest potential rather than old, degraded fluid. That being said, it is not necessary to flush your brake fluid. I am an ASE certified master tech with 20 years experience, and a GM master tech for last 14 years.