not sure if this is exactly the right place to ask but figured at least a few here will have done the upgrade, looking...

I assume you mean how do you build a pc? if you're really not sure I'd suggest starting with a pre-built pc, there's many companies out there that admittedly at a higher cost than self-built will provide a pc built, set up with windows and usually under warranty too, as far as installing in your home, you'll have power leads, internet if you plan to connect wired or get a pc with a wireless adapter to connect to wifi, in addition to a pc tower/case you'll also need a monitor/screen, keyboard, mouse, ideally a mouse-mat under the mouse and should you so wish, a headset/speakers, as far as storage I strongly recommend having at least 2tb of storage, Ideally on an ssd instead of hdd as they're faster, quieter, and last longer. hope this helps.

have you tried different cables, different power adapters? does the power adapter and cable work with your other devices? is it possible there's dust etc inside the port? it's possible that all they did before was clean the port out with compressed air in a can or perhaps after disconnecting the battery to eliminate the risk of shorts may have used IPA to clean out the port carefully with something to probe it, if that is the cause then probably wanna invest in some plugs for the charging port, I have silicone ones for my devices and it's great for keeping dust and any accidental splashes from getting in the ports.

might sound like a stupid suggestion but keep an eye out for cheap garden lights on sale or even ones that a friend or family member has had in their garden and stopped after a cold winter, this is usually just the batteries that have given up, the panel may still be salvagable