Rain Soft Older models

I recently had my unit serviced, I was told the O rings were binding up, and that the valve (which has a teflon coating) was worn and needs replacing. Is there a manual with an exploded view of the head available. I have had the valve bind up again and was considering making a new valve out of teflon. I just want a guide for dis assembly I own a precision machine shop and can make this repair on my own