Bridges

I have a number of ATX supplies that are dead. I want to try to repair them, instead of spending more loot on replacements. What I'd like to know is , what are the most common parts that you need to repair ATX power supplies? I know, a lot of electrolytic capacitors. But what kind of diodes...

This is my motherboard: https://www.newegg.com/p/N82E16813144214?Description=z390m&cm_re=z390m-_-13-144-214-_-Product The spacing between the GPU slots on the motherboard are 2-slots but I cant seem to find any 2-slot Nvlink bridges. I can only find 3 or 4 slot ones....

I have a dell computer it says the hard drive is a scsi i want to replce my old hard drive with a ssd drive but they all say sata how do i know if its compatable