The problem with these groups is that there are many questions and
very few answers. To clear my conscience from a previous posted
question, here's an unsolicited answer that might be useful to someone
down the line:

You can rebuild your Moen (and other manufacturer's) faucet valves by
cleaning the existing parts well and then reapplying the RIGHT KIND of
o-ring grease. Unfortunately, places like Home Depot will mindlessly
sell you "plumber's grease" in little white tubs from companies like
Rec-O-Seal which are NOT for use on rubber, but don't say that
anywhere on the container. These petroleum-based greases will cause
the valve to stick if not used for a couple minutes, although if you
work the stem it will temporarily appear to be well-lubricated.

If you buy grease that specifically states "silicone grease" or "for
use on rubber o-rings", it'll work like new and you'll extend the life
of your value indefinitely. My valves are 20 years old and work as
well as a new valve insert, and the o-rings are still like new.

That being said, if you are a contractor and can pass off the cost to
the homeowner, the $13 inserts are the way to go. But as a homeowner,
I saved about $150 in parts alone by redoing the valves myself.