Desoldering defective graphics card

Hello!

My MBP 2012 Retina went black while surfing, and none of the usual solutions (Shift+ctrl+opt+pwr, NVRAM, hard reboot, connecting separate monitor etc) worked. It’s not responding to either Caps Lock or Brightness adjustments. I’ve asked both Apple-certified personal as well as a general PC-repair company, both assumed it was a defective graphics card.

As far as I’ve understood, these are soldered to the logic board and thus hard to replace. My question is: would it be possible to desolder the old graphic card(s) from the logic board and replace them with new ones, as far as these new ones are compatible with the CPU? The internet has provided me different kinds of answers, so I’m not too sure as to what’s correct.