for the VNC server, if you haven't done so already, type vncserver :1 for example and using a viewer to start try hostname:1 with vncviewer. The thing with the VNC as far as I can tell you need to start the sessions first before connecting to them as well as modifying the .xstartup file or whatever its called in your home drive to load the X shell or whatever else.. I haven't been using VNC for very long myself. I tried some utilities like metavnc and some others aside form the one that goes with fedora.
I just setup a different utility built in to fedora using XDMCP. By itself is pretty unsecured but I got a program called FreeNX server/client and the NX client for windows. These are the links for it
http://www.nomachine.com/download.php -- Free NX Client (Windows)
http://freenx.berlios.de/ -- Free NX Server / Client (Linux)
Fedora how tos:
http://fedoranews.org/contributors/rick_stout/freenx/
It connects to the system through an SSH tunnel and then the NX uses a secure key before connecting to the XDMCP session.
Cheers