303,707 is a power supply fault.
393,320 is a failed developer motor.
"Error in Xerographic system" is the developer/drum typically.
My stab-in-the-dark here is that the machine is either plugged into an outlet that is faulty, or that it got hit by a surge and sustained damage.
You can try just shutting it down and removing the drums (All 4) and re-seating them, use the cleaning wand while you are in there and reboot.
But, you most likely will need a tech visit.