Back when Mac Classic was the Operating system for Apple there was a good book that was almost required if you wanted to fix Macs called SE Repair and Upgrade Secrets. It was written by Larry Pina and it went into detail about how to repair and upgrade a Macintosh Classic and Macintosh SE personal computer, without spending more money than would be required to buy a new one.
When did we start working on Windows. Our first version of Microsoft was DOS 1.0, Today it is Windows 10.x. They are losing a lot of market share, not something anyone predicted would happen but Apple has done everything right. However we will always have to support Microsoft and we know it well.