[el ess A]

If it ain't broke, don't break it. This is JMO.

That is a separate system. If your handle and cables and parking brakes are working like they should, there's no reason to change them. If you're doing your hydraulic side anyway, it won't hurt to inspect them for cracks, deterioration, problems. But if they're in good shape, no reason to replace them unless you just want to spend some $$.

If the rotors have not been trued on any of those brake pad replacements, you may want to at least think about doing that much. You can at least inspect them and check them.

IIRC, 32 mm is the new thickness of the front rotors. 30 mm is the discard thickness. 28 is new thickness of rear rotors, and 26 mm is the discard thickness. I thought they were marked somewhere on the rotors of this measurement. I could be wrong.

My rule of thumb on that is if they're within 1 mm of discard thickness, get new rotors. If not too wobbly, and greater than 1 mm of discard thickness, try truing first. Rule of thumb- turn rotors every other pad change. Unless terribly scored, etc.

Rockauto has the GM rotors for about 600 per complete front/rear set.

AC Delco p/n 177-1050 (GM#92245928) fronts and (GM#92245929) 177-1051 rears (super pricey).

If you really just have to have the parking shoes, they're GM p/n 92234842, but spending $70+ for them seems a bit excessive if you don't actually need them.