Salvage small LCD for system gauge?

Strange question maybe and I'm not sure if this is the perfect subreddit or not, but I figured I would start here and see if anyone had ideas.

I've seen some custom case mods that have small LCD screens on the front of the case for displaying things like CPU load or temperatures. While I'm sure there's probably some company out there that sells these for exorbitant amounts of money, I prefer to be DIY if I can.

So I was thinking. I have stacks of old defunct cell phones, gameboys, you name it sitting around. Lots of fairly nice 1-5" color LCDs. How hard would it be to re-purpose one ore more of these into displays for the pc. Where would I even go about looking into this. I've tried googling around a bit, but it's hard to find the right phrasing for the question.

If anyone has any ideas, that would be great!

I would say I'm intermediately skilled when it comes to computer hardware. I'm not afraid to open up a computer, I built my own. I've soldered peripherals together to change wire configurations and such. I wouldn't say I'm capable of building my own PCB that I would be comfortable attaching to my actual computer though.

Thanks in advance. :)