Possibly. Pick up a pressure gauge - cost about $10. You can get them with a hose connection - hook it up to your washing machine supply, water heater drain, a hose bib, or with adapters, in place of the aereator on a faucet. If the pressure is higher than set, or if it creeps up after water is turned off after running AND your expansion tank is not shot, then it's likely the PRV.
Whether you can do it yourself depends on your soldering skills and whether the house shutoff valve actually shuts the water flow off. Not sure if the ones available at HD are the best...just don't know.