I have the same Mobo and I updated my Bios when I upgraded to a phenom 2. I believe I used a utility that I downloaded from the Asus site. I had a number of of Bios versions to upgrade through to get to the one I have installed. To be honest I even got an error message during the process but I was still able to upgrade to the Beta version that I needed.
Anyhow like henydiah says I would only upgrade your Bios for a specific reason (in my case to support the CPU I wanted to add). I would be very surprised that a different graphics card is a reason to upgrade your bios.