'''I agree with the Genius's assessment of your problem.''' ''Though how/why the VGU/VGC or logic board became damaged in a simple RAM upgrade is troubling.''
You can purchase the parts and DIY (that's why we're here).''' This is a very advanced DIY project.''' You need the recommended tools'' (every job goes easier with the proper tools)''.
You need to study the guide for your machine so you know the warning and cautions '''- most failures for this type of repair is when the DIYer damages parts by tearing/breaking/ or doing other damage because they didn't disconnect something in the proper way.'''
You could check with local computer repair shops on their charges for the repair.
You could part out or sell for parts the damaged machine - and put that money along with what you'd spend to repair this unit towards a new machine.
Only you know your capabilities and budget.
Good Luck,
''If this Answer is helpful '''please remember to return and mark it '''Accepted.''