Yes. Have a plumber replace the faulty main valve with a ball valve.
It took one hour and the valve was about $25.

Will this involve smashing the tile behind the two valves?

The failure of the main valve is whats freaking me out because I might
need that .. and that worked a year and a half ago. But this is an old
building so ... (1970's in a way its great since its all brick, and not
wood like they make nowadays ... in another is bad since a lot of the
pipping is wearing down)

I take it plumbers can replace/fix valve without tearing the tiles out?

If the tiles have to go then so be it. I am just thinking how much it
would cost to replace tiles in addition to all else

I have a feelign this is gonna run into the hundreds if i am not careful