Is it possible to replace my motherboard, processor, and graphics card?

 

I've seen video where people removed their graphics card and put in a new one inside their laptops. I was wondering to do the same on said hardwares.

It is possible, but the motherboard would need to be the same and depending on whether the graphics card is soldered to the motherboard, it should be possible or not. You should be able to replace the CPU if it isn't soldered to your motherboard.