Set Screensaver Programatically
Running this following line of code in Terminal will set your current screensaver to "Arabesque" with a delay interval of 600 seconds.
osascript -e 'tell application "System Events" to set current screen saver to screen saver "Arabesque"' -e 'tell application "System Events" to set delay interval of screen saver preferences to 600 -- Number In Seconds'