1958 Impala heat control valve

I am helping my father-in-law with his Impala and we couldn't get the heat to work. We took the valve out and determined it was froze up. Can someone school me on how these work and recommend a place that rebuilds them.

Thanks, Tim

http://www.heatercontrolvalve.com/

or

http://www.heatervalves.net/index.html

or

http://www.classicautoair.com/

You should have no problems