As far as a list of all models of every Mac gadget and it's OS and specs.. there is Mactracker.
It is free and AFAIK gives data on every device ever made by Apple.

For technical repairs, that would be another matter. Maybe you should team up with Mactracker and do the other half of the equation.. the technical repair/troubleshooting part.

To keep up with all of Apples products and specs and troubleshooting and repairs/problems, etc. is more than a 1 man job in my estimation.

A society grows great when old men plant trees whose shade they know they shall never sit in.