"Is my power brick dangerous?"に関する回答the white light on the power brick stays on if you have the "instant on" option ticked in the settings. And if you have to use a hair dryer to power on its probably best to just replace it they're not expensive.
"2011 iMac potential GPU failure, worth replacing?"に関する回答Its a standard laptop part called MXM. The GPU you can upgrade to a newer mobile GPU like the GTX 980m for less then replacing it with another HD 6950m that will fail again in the same way