This is the first time i using mac os so any tutorial for that?
Their solution is wait for update 10.8.5. So should i wait?
Then wait for it.
It should be out anytime.
As for why your Mac gets hotter when you run Youtube.
It's because Flash runs badly on anything except on a Windows Operating system. Consider viewing youtube on HTML5 instead.
www.youtube.com/HTML5
And don't remove your VGA driver as advised by havetobuy.
There's no way to download a .kext (driver) on Apple's website and chances are you'll ruin your operating system if you have no idea what you are doing.
Apple issues their driver updates via the App Store.