I have a 3 handle moen shower control installed on tile wall. Just bought my first house last week so no idea how old unit is. The middle knob (shower diverter if I researched correctly) will not turn. I have tried taking off handle and using WD40 as suggestd on one website and still no luck. I found another website that said but new diverter at hardware store. I was told at Lowe's and Home Depot that if more than 5-6 years probably no longer have part. I believe the bathroom was added on house in 1997 or 2002 so probably that old. Will a plumber have to remove my tile wall to replace faucet? If so does anyone know a rough ballpark of what something like that might costs?