I just got a D630 and I got dual head working by installing the proprietary nvidia driver and used the Nvidia Display Settings found on the gnome System Tools to configure the dual monitor.
One problem I have is that the gnome panel seems to want to only reside on the external monitor. I haven't yet tried to hack the xorg.conf file that this utility generated. I still have some work to do get it just perfect.
$ rpm -qa|grep nvidia