Kitchen sink sprayers are easy to repair. Instead of repairing one, though, you could install a one-touch faucet.
If pressure is low make sure the hose is not kinked. If that's not the problem, disassemble and clean the sprayer. If that fails turn off the water and check the diverter.
If water comes out of the sprayer even when its valve is not depressed, replace the sprayer body and valve.
An hour or two for most repairs
Screwdriver, groove-joint pliers, long-nose pliers, toothbrush, knife
Dismantling and reassembling a unit with small parts
Shut the water off only to work on the diverter valve; lay down a small towel for organizing small parts
Replacement parts for the sprayer and diverter, perhaps a new sprayer, silicone grease