2001 GMC Sierra Heater coil hose connector

Im writing to ask how you would remove the pipe sleeve cover that the hose connects to for the heater coil in out. The extension that slides into the hose broke off due to age and I cant get the Sleeve off. I went to auto parts store and they said to bring the part in. I cant get it off to do so. The in outs are next to each other, left is black the right is off clear. Any help would be Gratefully recieved.