If it's the heat sink issue, the solution is to remove the heat sink and replace the "silver paste", I think that's what it is called. This worked for me for about 6 months. Since you're this far you may as well try it.
Another trick I saw and did if you didn't take it apart: Take a Qtip and jam the cooling fans in the back. Turn the unit on, in about 5 minutes it goes into another failure mode (I forget, it might be blinking lights). Power down and restart the machine. It actually works. I think it puts the unit into a overload reset mode. However, this doesn't actually fix the heat sink issue. I got 6 months out of doing it this way too. Found it on youtube by some 10 year old twerp.
