Hi. My name is*****'m a camera repair technician with over 20years in the business and I'll be glad to help you with your question today.
I'm familiar with the M68 projector and this one sounds like it will need some work to get it running again. Unfortunately, parts are scarce and qualified repair techs are hard to find. In the long run, it might be cheaper to have a service transfer the film to DVD or buy another, good, projector.
The Instamatic projectors were very popular once. They're pretty straight forward. Put it in forward and stick the film in one end and it comes out the other. I should even start itself on the take up reel.
The problem is, the belts wear out, the clutches need servicing and usually at least one of the thin plastic parts need to be replaced. Believe it or not, you can still get belts for these, you just can't get technicians to install them.