Per a GM tsb there are updated shoes and retaining clips.

 If you have not used your 2000 Emergency Brake for parking on a weekly
basis,

 the 'brake shoe in the disc brake hat' might have caused a 1/8" rust
ridge

 on the parking brake drum.....     It's a tough job to remove the
outer disc

 brake rear unit when trying to get at the parking brake shoes....

 Bigger hammer,    might not work well while causing damage!

They are not pads, they are shoes.  Removing the brake caliper
and rotors will be the first step.  If (as another poster mentioned)
you have problems removing the rotors due to the afore mentioned
rust ridge, you can try one other trick that I've used.  Drive out one
of the wheel studs (it will fall inside the rotor and you can retrieve
it afterwards), turn the rotor until the hole where the wheel stud
was lines up with the 8mm/5/16" bolt that hold the shoe to the
backing plate (the hole will line up with bolt), remove the bolt and
then try to take the rotor off.

Once the rotor is off, you will see how the rear shoe is retained
and adjusted, fairly simple from there.

Ian

I was charged $160 to have my emergency brakes replaced on my '01 Silverado
1500. The parts were $56 if I remember correctly. It wasn't a huge job (I
watched). When it was time to repair the emergency brakes on my 3500
Sierra...that was an entirely different matter.