This is insanely expensive, and again, just putting defective parts into service. The final option is to replace the logic board. Replacing the GPU is very dangerous (brick warning), and you are just putting another defective unit on your board. You can extend its life for a few weeks with a reflow, or attempt to replace the GPU. You are not going to be able to fix the GPU. There is a widely known defect in the Radeon GPUs on these MacBook Pro models.
This is normally lines on screen, stripes on screen, sometimes even black screen or blank screen.
So you, like many others, have a 2011 MacBook Pro with video issues.
