Should be no major problems so just a few points:
The GTX680 is a powerful card, it'll benefit from a CPU overclock, not essential, but something I feel you should look into ( my i5 750/HD7950 rig benefitted significantly from a CPU overclock), just a thought.
If the power supply is as old as the rest of the build you MIGHT want to consider replacing it, especially if the GTX680 needs 1x6 and 1x8 pin PCI-E leads and the current unit has 'only' dual 6 pin leads, power supplies do lose efficiency and output over time (Google 'capacitor aging) so if it's borderline a replacement would be a wise investment.
When swapping chip makers, it's a good idea to fully get rid of the old drivers before installing the new hardware, DDU (Display Driver...