Is the body set to AF? Does the lens have an AF/MF switch and set to AF? Try cleaning the contacts on the lens and mount and/or a different lens.
Otherwise parts is going to be the problem if you can find any place that will work on the camera.
You can try the repair company in Japan run by former Pentax technicians and engineers. Another forum member had his/her MZ repaired by them for the mirror lockup problem. Reports are this company seems to be unresponsive to email requests.
Lens Repair Co. run by Retired Pentax Engineers - PentaxForums.com