My PS3 died too after nearly four years so no warranty comeback.
I followed [http://www.youtube.com/watch?v=U70SgRDVcBo|This Video] on how to fix it.
I didn't have a heat gun though so I searched a bit more on the internet and found [http://www.youtube.com/watch?v=bDu9ePWF4gg|this video] from the BBC consumer affairs program Watchdog.
So I googled to see if anyone else had tried using an oven to do the repair. The general consensus seemed to be around 400F for 10 mins.
I didn't have a tray so I wrapped the motherboard in tin foil and stuck it in the oven (pre-heated to about 400F for 10 mins.)
I then let it cool down for 20 minutes and followed the video again for re-assembly.
Worked like a charm for me PS3 is working perfectly again.