Earlier quoted context omitted.
Highly skilled? I don't think so. You just have to be very careful, and pay attention to the right things (ESD, cut the power, short circuits, etc). Secondly, the diagnostic needs to be correct. Multiple faillures is unlikely if there is no external cause (surge, flooding...) or cascading failures. Both of the above points can be solved with good documentation. I've seen very good servicing manuals, this is part of t…
I think your reply shows that you are already very skilled. Other comments mentioned replacing a diode -- I know what a diode is conceptually, but I have no idea how does it look in the appliance, where would I buy a new one or how to replace it. Being as clueless as I am, my only option is to call a proffessional. Sometimes it is worth it -- I had a fan on my MacBook replaced for ~700 SEK which is a fraction of the…
With good instructions, I can set out to repair mechanical parts as well (replace parts of an engine for instance), high-voltage devices, masonry, or other stuff I have never done before.
A good manual can make the whole difference between a successful repair, dealing a finishing blow to a product, or endangering yourself/others.
Making repairs easier probably makes them cheaper as well (less skilled employees can attempt them, it takes less time and is much more enjoyable). I know I would charge less.
Of course, the product has to be designed to make repairs possible, otherwise it requires a whole other level of skill (unglue parts, precisely cut where you need to).
And lastly, you can only go as far as your equipment will allow you. Sometimes all you need is a (included) screwdriver, but not everyone has a milling machine handy (though that would be an interesting use-case for fablabs).