There is a great article with pictures, diagrams and everything in the manuals and catalog section. Look under "US Divers manuals, testing, parts drawings, all years covered" and go to the file on J60 and J62 Valves. I have rebuilt several and it isn't rocket science. Most parts are reuseable. There is a black gasket in the J-Valve seat assembly that is usually toast and hard to come by but folks seem to get by with a similar size o-ring instead. Should the Teflon Valve Stem Gasket in the Reserve lever assembly need replacing (it hardly ever does), I think Bryan has them in the web-store. If you tell him exactly what you are looking for (i.e. part number from diagram) after you get the manifold apart I'm sure he can advise if he has it. Don't forget new burst discs of the correct pressure rating for the tanks you intend to use and use the proper in/lb torque to install.
Good luck with the rebuild. Mark
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968)