Replacing a broken sprinkler head, valve, or solenoid is something you can do yourself. All you need is a few tools like a shovel, a PVC pipe cutter, a wire locator, a PVC solvent, time, and elbow grease.  If it is a mainline, you will need to make sure you use PVC primer for lines under constant pressure. Make sure to call 811 before digging to know where your local water, electrical, and utility lines are located.