I have a 12 year old Moen shower (only - no bath). Single centered handle - left for hot, right for cold, all the way right for off. It developed a drip from the head. I popped the center logo cover and unscrewed the plastic tear-shaped handle. Found it was broken inside. Happily, I replaced it, thinking it wasn't turning the valve all the way off. Nope! New one installed - still leaking. So, now I think its either the cartridge or (hopefully) there's a washer on the back of this whole thing and I can get away with a $1.50 repair! Anyway, I've pulled the 'N' shaped metallic retaining ring, but I cannot get the cartridge out. A few questions...

Am I on the right track?
Is there a special tool to remove the cartridge?
Do I have to remove the round chrome faceplate behind the handle (hope not - this is secured with 2 screws and silicone)?

Forgot to add - I bought one of those wrench sets - looks like a spark plug wrench, to remove the cartridge but there is no room to slip this around the cartridge.

Thanks... ANYone!! LOLOL

"Is there a special tool to remove the cartridge?"
Moen does make a cartridge puller,(see image) for those stubborn cartridges.

Do I have to remove the round chrome faceplate behind the handle (hope not - this is secured with 2 screws and silicone)?
You do not have to remove the face plate to get at the cartridge, however you will have to pull the chrome stop tube off.

After you turn the water off and have a open valve body turn the water back on for a minute to flush out any debris that may be in there. N ow you can install the new cartridge.

No, there's no washer in there and the replacement cartridge will set you back more then a back and a half. Good luck, Tom