I have a shower/tub combo with a faucet kit that has a head, control valve and trim and bottom spout. The shower control valve unit (center-piece) has a difficult time turning off and instead of buying a complete shower faucet kit with two pieces I don't need, I would like to buy just a new control valve (innards) and a new more modern looking trim piece, perhaps a chrome lever handle, instead of the plastic trim. Is it possible to buy only a replacement valve and a new modern trim piece? The unit is a Moen and about 10 years old but I don't know the model number. I looked online at the big box stores' online catalogs and valves can range from $10-$60 and I have no idea what kind I need. New three piece shower/tub faucets range in price from $50 to $400 and I have no idea on quality differences between the models. It's kind of frustrating.