I've never done it on a K2XX but I did replace all of them on the avalanche. Based off everything else I've noticed, they are very similar. IIRC, when I did the rears on the avalanche, I somehow bumped a plug and it came loose. Started it after the install and had "service suspension" light on. Quick google and saw that a lot of guys had done the same thing. Climbed back under and sure enough, it was unplugged. Just pointing that out, in case that happens to you. I believe it was on the drivers side.
Another thing. I replaced the shocks and compressor because it was coming on a lot more than normal. That didn't change anything. After more research, I found the line that runs to the passenger side (inside a harness), had a pin hole and that was causing all of my issues. Being as the dealer diagnosed your shock as bad, I'm sure that's the issue. Good luck on the swap!