Hawk, While you ponder which manuals to get to help you with working on your truck, take a look through the publications throughout this
Keith Hardy's OLD ONLINE CHEVY MANUALS.
It is an extremely handy source page. You will find shop, parts and owners manuals available to peruse as well as other technical source documents that will be of great help to you. Unfortunately nothing about the dump hydraulics specifically.
For questions on those though, you could probably post some questions about them and other "Big" truck related specifics in our
Big Bolts forum. We have many Bolters with hydraulic dump systems which may be able to help you with questions or repair needs.