The text disappeared... Here again:

My main shower is old and in need of updating. The shower is a single handle valve. The gold finish plate over the valve has a SA stamped on it which apparently stands for American Standard. At any rate, the valve works fine but I was wondering about update or upgrade options. Without tearing into the wall can I find the correct updated trim packages available today?

I suppose I would have to tear into the wall to replace the valve?

The existing main bath is entirely builders grade fixtures and I would like to upgrade but dont want to tear-out.

What to do?

That little mark on the bottom is a CSA stamp, Canadian Standards Administration or some such. Kinda like a UL stamp in the US.

Dang! How do I swap out the hardware? I want a handle rather than a screw out plastic knob to turn on and adjust the water. How do I know what is compatible?

Remove the handle and the base plate and go to a plumbing store or your local Home Depot or Lowes... You find replacements without knowing what brand - there are all sorts of adapters and ways to figure out what the inside spline is like...

The whole bath has served it's time. It's of an era where best practices were in flux, and you have a really good chance of having moisture behind the walls. A 30 year old valve with no scald control shouldn't ever stay.

Time to gut it and redo it all.