[CentOS] Changing Window Mangager in X

Hi. I've been running CentOS 4 since it was first released. I just updated (via yum) to 4.3 yesterday (with no problems as most would guess!). My system runs X on start up (initlevel 5) and uses gdm as the display manager. I know that when I first installed CentOS 4 with GNOME as the default desktop, it came with metacity as the window manager (in fact it is still installed and I've never touched any of the X settings). I would like to try another window manager (I saw one in the CentOS extras repository). Can someone sort of guide me as to what I need to do to "run" a different window manager in X? The window manager that I want to try is 'xfwm4'. Thanks.

Sincerely Jose