XDM or GNOME???

["spider" <bziku@spider.ds11.agh.edu.pl>]

i installed potato on my machine, and i had XDM as the window manager.
i wanted to switch to GNOME, so i put:
        exec gnome-session
in my .xinit file (/etc/X11/xinitrd/.xinit --- i hope its the right path...)

1. did i do the right thing??? i mean is it the right file?
2. there is this GNOME panel and icons on the desktop, but i dont have an
arrow as a pointer but this black cross...
AND- when i shut down X server there are those messages going, and the last
one is:
        shutting down the xdm display manager

im confused cos i thought i was running gnome dispaly manager....

please help me with this awfully simple problem...