If you remove the handle and the cover plate, you will expose the valve. The cartridge that is held in place by a retainer, is replaceable. Remove the existing cartridge and take it to a Home Depot, or a large hardware store. They should be able to identify it. If not, you may need to try a pluming supply store.
The valve will look something like the photo. The steel thing with the loop is the retainer, although there are some that look different. Pull the retainer up an off, then pull the cartridge out.
Retired electronics engineer. Avid paddler & birder.
2011 Silverado 2500HD, diesel, 4x4,crew cab, 8' bed
Palomino Puma 253FBS (27' 5er) & '94 19' Class B