Complete flush with a cleaner made for AC systems, don't get the cheapest stuff. The good stuff is expensive but its worth it. To do the flush you have to take apart.
Before you put it back together replace the o rings. You also want to replace the orifice tube. After all that it needs to be vacuumed down before new oil and refrigerant is added.
Oil is done by volume. Refrigerant is done by weight. I would use Esther100 because it plays nice with any mineral oil still left in the system and works fine with 134a.
If you have the fancy machines the oil is added with the refrigerant. If no fancy machine you have to add it to various places of the system before you do the vacuum step.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.