What specifically are you having problems with? Bleeding procedure or possible faulty parts? Is it pedal problems? The hydrovac diaphragm does go bad and allows fluid past and into the vacuum line which can then be sucked to the intake.
If it is faulty parts, very few (if any) local shops have the know-how for a truck that size and age let alone ability to repair/rebuild and replacements don't directly exist. Good reputable shops can rebuild your current unit, but you have to take it off and ship it out for the rebuild. If you go this route, it is best to have them do the master as well.
