Yes. A PCI Express 3.0 graphcis card can work on a PCI Express 1.0 graphics card. There will be no performance difference too. If there was, it will be not noticeable.
This is mainly a gimmick in my opinion.
Edit: Sorry, just saw you had your problem solved. But if my answer help, then it may have provided a bit extra information too.
Yes. A PCI Express 3.0 graphcis card can work on a PCI Express 1.0 graphics card. There will be no performance difference too. If there was, it will be not noticeable.
This is mainly a gimmick in my opinion.
Edit: Sorry, just saw you had your problem solved. But if my answer help, then it may have provided a bit extra information too.