Get the gm unit repair manual for the year the trans came from. You should be able to find them on eBay. The unit repair manual was the deeper dive manual over the normal shop manuals. Unit repair only goes through tear down and reassembly of components like the engine / trans / t-case / diffs.
I picked up a used one for my ‘91 on amazon. Very handy as they will have the exploded view a well as all the specs and step by step process to take it apart and assemble it.