FWIW,
When i was workin on my automotive science degree, we had an electrical portion where we talked about this same topic.
Instructor gave the class a choice of rebuilding one AFTER we considered the options (cost,time, and availability of parts)
It was a no brainer after all the facts were considered(especially warranty) that as a class we chose to NOT rebuild one,Though we did cover"theory".The time was better used diagnosing electrical "bugs"planted in the class project.
Now that i look back, i wish we would have actually done one just for the sake of knowing how to do it.
BTW, i too looked at buying a rebuild kit for my 89 and i didnt find a place that had all the components at a remotly reasonable price.