Replacing ATI card w/ nVidia card

My ATI graphics card's fan died, causing my graphics card to overheat and shut down the PC every time I played CoH. My friend gave me another fan to rubberband on top of the broken fan, and that's working pretty well, but noisily. So I bought a new nVidea card with a passive heatsink that I hope will be both quiet and long-lasting.

My question is, since the new card is nVidea and not ATI, does that mean I can install the nVidea drivers without having to uninstall the ATI drivers?

My friend recommended that I (1) boot up in safe mode, (2) uninstall the ATI drivers, (3) shut down the PC and replace the card, and (4) boot up with the new card and install the new drivers. Does that sound like the best plan? Is it overkill -- can I leave the ATI drivers alone? Or is it underkill -- do I need to run something like DriverCleaner after uninstalling the ATI drivers?

(And feel free to comment on whether I was stupid to get a card with a passive heatsink instead of a fan...when it comes to upgrading my PC, I really wing it a lot.)