directing the output of another PC into that laptops display or taking out the display and then plugging it in separately as a display?
first things first, the laptop display has a separate connector, sometimes proprietary. if you manage to find an adapter you could do this, but soldering won't be an option and it's nearly impossible to do with flimsy connectors with flex cables.
you could also direct the output through the laptops motherboard into the laptops display without disconnecting it, if the laptops mobo isn't fully dead and working. (no high hopes on this one tho)
finding an adapter would be the thing to do, and you could plug the adapter into the existing connector and plug the other end to whatever display out it's compatible with.
the display may need to be powered separately, but that's least of your concerns if you're attempting this. powering will be easy, finding the adapter would be hard, getting it to work is even harder.