slim server is not installed until you add squeeze box player device.
just add squeeze box player to lan and reboot.
because that device in pnp, you'll see on orbiter that pluto has detected the device, it asks for device template and for a room, where to be assigned. create a new room for squeeze box, since needs it's own entertainment area.
you'll need to reload and regen all screens.
to upgrade your system, you need just to reboot