How do I perform easy switching to external monitor
The nvidia tool nvidia-settings can be used from command line, but is not capable to activate or deactivate screens. xrandr is not supported by the propietary NVIDIA-drvers.
To switch displays you can use the tool disper: disper on launchpad It's a command line tools, wich exactly fits your problem an is easy to use.
Some example scripts for automatic switching at startup can be found here: Ubuntuusers.de wiki
I use these scripts to switch my monitors. It works perfectly.