John,
I was thinking about the tests you can do while the starter and generator are on the tractor. I was also thinking of the field coil, armature and brush tests done with the unit disassembled. The actual rebuilding of the units is probably more in depth than you might want to go into, but being able to diagnose a problem would help a lot of people. I think installing new bushings, brushes, etc would be self evident to most readers These are just suggestions. Since you're the one writing the articles, it's your choice. I just enjoy being able to make the repairs myself in this throw-away world instead of depending on someone else.
Geoffrey