Installed this over the previous weekend:
WABCO Compressor Rebuild Kit.
Install was easy, if a little fiddly. Lowered the truck to the bottom and pulled the associated fuses before removing pump. Very little air (if any) escaped the system when I disconnected the compressor air line. I managed to spill the OE dryer beads which was fun to clean. Only spilled 10% of them and it still took a good half hour to find them all (all the ones I could find anyway). I did this as a preventative measure since I am slowly working on my audio system and access to the pump is easier now than it will be later.
I was not having any EHC errors or other troubles besides sagging if the vehicle sat (long time... month). Figured for ~$36 it was cheap PM and my pump could probably use a refresh. Cylinder bore looked okay and the old piston ring did not appear too bad either, though there was some wear obviously. Fitted everything and had the pump back in the truck within a couple of hours. I did not disconnect the battery or anything while servicing. Upon reinstalling the pump and putting the fuses back in, turning the truck on, and engaging the system I thought something was wrong. Before I could distinctly hear the pump engaging but now it is almost dead silent with the rear cover on. I was not getting any errors on the dash or foxwell so I put it into the highest position and picked a horizon landmark for the hood and could see the truck go up... fast. So, everything is working great. Quieter and possibly faster than before the service. So this kit gets a
from me. Just thought I would share with you all in case someone else was interested.