Hey, I see your from Michigan as well. Hopefully you had your system winterized (blown out) last fall or you could be looking at some serious issues from freeze damage. If you properly winterized it, everything should be just fine. There should be a shut-off valve for your irrigation system near the systems POC (Point of Connection) which is probably near your water meter. Make sure all of your drain valves (if you have any) are closed before turning the water on. As for your broken sprinkler head, weather it is a rotor or a spray head, your better off to just replace it with something similar. The rotor heads, if the top is sheared off, are not repairable, and the spray heads are cheap enough cost wise, that when they break (unless its just the nozzle) they should be replaced.
Tony Posey
Ridge Run Landscapes