Recently, kitchen sink spray hose has begun a high-pitch squeal when in use. Easy fix?

Probably a dirty diverter valve. You will need to disassemble the body to get to it. However, try this. Pull out the spray hose and unscrew the sprayer. Point the hose into the sink and turn on the water. If you still hear the noise, it is most likely the diverter. If the sound goes away, clean out all the holes in the nozzle and soak it overnight in vinegar. If you hear the sound, take the faucet apart and look for a small spring loaded button on the side of the valve body. Remove and clean, soak in vinegar and reassemble.