As I already mentioned, I did that just the way explained above - but I meant update without me manually removing old and installing a new version of Firefox. Then I remembered that one cannot update CentOS like that, I just type # pacman -Syu in Arch Linux to get latest updates. However, I forgot that CentOS doesn't work that way, and I had to do it just like you described.
One more question, how do I make it show in applications so that I don't have to type firefox & every time I want to start it. I use KDE 4.