If you do not get the above error message replace the CMOS Battery and you'll have to reset the BIOS again and when you remove the battery don't forget to unplug the computer as just having it not running still has power to the M'Board and if you accidentally drop the Battery you'll ruin the M'Board. Get a new Battery Radio Shack should have the things and they are cheap then refit the battery the same way that it came out this is with the writing of the make and model of the battery readable when fitted in the M'Board and at the same time there should be a jumper just near the battery change it from 1-2 to 2-3 for a few seconds and then change it back as this clears the BIOS and then reboot and go into the BIOS set the Time & Date and any other Drives that are fitted and the boot sequence and then save the changes and exit. This should reboot the computer and you'll be up and running.
The sticking Key doesn't need any explanation as it is fairly obvious how to proceed there.
The only thing you really need to worry about is if the Video Card that died had a fan on it which has seized up it could have drawn more power than the M'Board could handle and this may have caused some damage to the M'Board if it didn't have a Fan on the GPU you'll not need to worry about this option. But even if there was a fan there provided you didn't replace the Power Supply with something bigger to stop the computer hanging everything should be OK.
If it still doesn't work after all the above you'll need to swap out the Power Supply and buy a good one like an Antec, Evermax or similar and at least a 450 W one as if there was a fan on the GPU the PS has most likely been damaged. The way that these things tend to go is the GPU fan fails then the computer starts falling over randomly and the PS is replaced with something bigger which then proceeds to burn out the M'Board.