Did my GPU die or something worse?

I have a Radeon HD 5770. Prior to a couple of weeks ago, everything was fine. Temps ran at a steady 60c at full load. Now, for the past two weeks, my temps went up to 100c with the fan running full speed. Two days ago, Sim3 started having artifacts on screen yet WoW ran fine. Then, the next day while playing WoW, the screen locked up and I received a message about the video drivers having an error. I uninstalled the video drivers to reinstall again (latest version) and now the PC isn't even detecting the card at all and when it sits in Windows for a moment, I lose video signal.

I've checked the cables, reseated the card, looked for signs of physical damage, double checked my PSU (which is no more than about 4 months old and everything is running fine) and now it drops video signal the moment it tries to boot into Windows. So, has my GPU died (the card is 5 years old) or something worse?

I've already ordered a new card, although it's an Nvidia. But, I worry that it isn't just the card. I worry that it's the PCI-E slot that's given out. Today I even tried "baking" the card, no luck.