If you put the WINDOWMANAGER lines into .profile you wont be able to log into any other window managers and other users will need the lines in their .profile in order to use KDE3, but You can get kde3 into the window manager options at logon by doing the following...
well first install all the KDE3 packages
click the K menu,
open control center,
then Login manager,
click root and supply the password,
click the session tab,
and in the field 'new type' under 'session types' type kde3,
then click add new.
On my system this could not be done from KDE3, I have to login to KDE2 in order to make changes to the XDM.
And mcujino If you dont have GNOME, use YAST2 to install it from your SuSE CD-ROM or downloaded RPMs and you can do the above for gnome.