Imac video card replacement?

Question

iMac

Yesterday an unpleasant situation happened, when watching youtube on Imac 21.5 (mdl 2011), the screen went blank, restarting the computer did not help, there was a gung at startup, the fan was heard and the drive was diagnosed.
As a result, I came to the conclusion that the video card burned out. Please tell us how you can check that this is a video card and not a matrix?
And a few more questions for connoisseurs:
1) Repair costs about 20 pieces in offices. I decided to change it myself, where can I find a new card? the specialist from the repair said that they supply cards from the FOXCONN factory is this possible?
2) What problems may arise during the repair
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PS: the reason for the inability to hand over to the service is expensive + a lot of information on the computer

Answer 1

You won't take it back