Moen, Replacing shower faucet fixture (not valves)

My kids and I currently live in a guest house, and the shower fixture has started to malfunction. You can't easily turn it on or off, or control hot/cold water. I've taken a photo of what I think the problem is. Does the location of the problem (looks like where the valve and fixture connect, mean the problem may be the valve, which needs replacing no matter how much I want to avoid?

I have some DIY plumbing experience. I've replaced leaking copper pipe with PVC under the sink, replaced shower heads and replaced a toilet. I absolutely cannot and don't want to handle valve replacement, but can't afford to have it done, and the landlord will not agree to repair.

The fixture is very small in size and says "Crane". Anyone know if this is something I can buy a compatible new fixture at at Lowe's, Home Depot or a plumbing supply store. What type of fixture should I look for?





If not, I will have to live with it I think, but I'd really like to repair.