The mamiya service manual is available from CameraBooks for $20
You can get a service manual from CameraBooks, they sell for $20. They don't show details of the lens but more of the body which is all good ingo, some is missing but can be figured out or by asking. You can get exploded views and diagrams from Mamiya for almost anything and they still have most of the parts. Call their tech department at 914 347-3300 and they will fax the diagrams to you, you can also order the parts you need.
These cameras are built like tanks and are easy to work on. Most parts are so large you can make your own by cutting up car fenders. MOst repairs on this camera are just adjustment or cleaning, hardly ever parts unless the camera was forced or physically damaged. they aren't as delicate as you might think but should not be pushed as that is how damage occurs.
If you ever need to repair, just e-mail me I'd be glad to help.