I have a Moen single-handle posi-temp shower faucet that is leaking. Based on Internet research, I determined that the cartridge needs to be replaced. When I took off the handle and the escutcheon, there is a white plastic circle that is blocking my access to the retaining clip. Looking at the parts diagram on the Moen website, I think this plastic circle is the "plastic ground." I cannot remove this piece, as the hole in the shower wall is not big enough to get the piece through it. My question is if I am going to need to cut a bigger hole in the shower wall in order to take this piece off so I can get to the retaining clip and cartridge. If so, how can I do this without damaging the plastic ground, or should I just purchase a replacement beforehand and assume it will be damaged in the cutting?
I am a complete plumbing novice, so thanks in advance!