Chosen Solution
How can I fix that pressed power button from top? Is it something I can do without it costing too much? It looks like it just got unhooked or displaced from its place. Not broken where a piece broke off no.
If you cant repair it yourself, I suggest you get another momentary switch, then solder it to the wires connecting to your previous one. Momentary switches similar to the one used in your PC case is cheap. it can cost for less than a dollar. It may not be the exact same kind of switch but it should do the trick.
