Replace GPU on iMac Early 2008?

[MacNewbie1234]

Hello!

I have iMac Early 2008 with 20inch screen-
So i have a question i have Radeon HD2400XT 128MB and i have feeling that the gpu in dying (light vertical lines)...I have Yosemite 10.10.
Can i replace the gpu with better or existing one (working)?
Is this a hard or easy job? Where i can find any tutorial?
Lines:

Is this screen or gpu problem?
Thanks in Advance im new on this forum and this is my first Mac!

Best Regards!

 

[scottish]

I have no idea about most of your questions, however, here is a guide if you do decide to go ahead: https://www.ifixit.com/Guide/iMac+Intel+20-Inch+EMC+2133+and+2210+Video+Card+Replacement/1014