You can download the service manual from here:
Pentax Manuals
In most cases with manual focus cameras the dials and levers need to be removed before the top cover can be taken off. You will need special tools like spanner wrenches, JIS and small slotted screwdrivers.
You could try Eric Hendrickson, who repairs MEs:
Home-Pentaxs
You may want to review the various discussion threads concerning him first.
Or try some of the repair facilities listed here:
Pentax Repair Facilities (Wordwide listing) - PentaxForums.com
Advance Camera and Garry's Camera Repair come to mind as those that would work on an ME.