You are correct.
Well, of cause. If you break it, it's your fault.
Assuming that you purchased the parts from reputable sources, these parts should have their own warranty.
The parts should have their own warranty (Assuming that you purchased the parts from reputable sources)
Absolutely. The display is basically just a big piece of glass held on by double-sided tape.
Assuming that you can handle a glass table top without breaking it, you can absolutely handle the display.
Here are some images of my upgrade
:
https://forums.macrumors.com/threads/imac-27-inch-late-2013-hdd-ssd-upgrade.2122595/