How to proceed when switching from ATI to nVidia (new GPU)

Hello.

I am sorry to ask something that might sound silly, but I am wondering what the "best practice" is for replacing a GPU.
In my particular case, I am switching from a HD 5870 Crossfire solution to a single nVidia GTX 580 Twin Frozr card. Without attempting to fan the flames of that peculiar war, I have found that I am not happy with the drivers from AMD and that my motherboard's PCIe slots are just too cramped for two hefty cards. I know that I lose performance and that the Crossfire solution generally offers good performance, but the truth is, I just can't handle the hassle with the GPU @ 100 % when idle bug etc etc etc.

So what do people when switching?
I have backed up my system, and have downloaded the 266.xx drivers for the nVidia card, and plan to uninstall and driver sweep before physically replacing the GPU(s).

I have no idea whether it is necessary, but better safe than sorry.

Are there any issues regarding the replacement I haven't considered?

In advance, thanks.