Woodford Valve Seat Question

Hi, My Woodford Model 17 silcock developed a leak around the stem and also would not shut completly off. After fully tightening the packing nut in an attempt to stop the leak around the stem and still seeing a leak I ordered the new EPDM packing and valve seat rubber (to fix the leak after the faucet was completly shut off). Over the weekend I disassembled the faucet (with the help of some information on found on this forum) but when I attempted to replace the valve seat rubber what was on the faucet did not resemble the part that I had ordered. What I noticed on the faucet is a small bit of rubber around the retainer screw head. It looks like some sort of tiny O-ring embedded in the metal that the screw screws into. I removed the screw but did not see any way to remove the tiny O-ring. I attempted to place the new valve seat rubber over it and screw in the retainer screw but the old screw is not long enough to make contact with the threads with the valve seat rubber in place. So, how does one replace the valve seat rubber on this faucet? Do I need to remove the manufactures little rubber ring first? Should I have ordered the retainer screw (which is maybe a little longer) along with the valve seat rubber.

Replacing the packing was easier but I also had a question about that. The old packing was (i think you call it) wicking and the new is rubber. One side of the rubber is concaved and the other side flat. Does the concaved side face toward the handle? I installed it that way and the leak around the stem is now fixed. Just want to check on the correct placement of that piece.

Thanks in advance for your help.