For the server admin tool see at http://support.apple.com/kb/HT1822 .
The 'xgrid sharing' option is only provided to allow access to your computer from xgrid controllers, in order to distribute their tasks. You don't need it for your purpose of setting up an xgrid controller.
If Xgrid lite won't start the controller you either need to verify that the installation of the xgrid controller components has been done properly or you need to provide a working copy of the client and agent password files.
In the first case, try the following:
1) verify that you have access to the directory /var/xgrid
2) under /var/xgrid, rename the directory 'controller' in 'controller-old'
3.a) start the xgrid controller with xgrid lite, or
3.b) run the command sudo /usr/libexec/xgrid//xgridcontrollerd to start the xgrid controller
the previous point (3) will also create a new copy of the directory 'controller'.
4) at this point, try connecting to the xgrid controller using Xgrid Admin
If you can't connect, set a working copy of the client and agent passwords in the following way:
5.1) go to /etc/xgrid/controller
5.2) rename (if any) agent-password in agent-password-old
5.3) rename (if any) client-password in client-passowrd-old
6) set the client and agent passwords with Xgrid lite
7) At this point, try connecting again with Xgrid Admin
Hope it helps.
Cheers!
Carmel