Help with changing preferences with applescript

Hi,

I'm trying to create an applescript app that would change setting on the computer to my desired ones. I've figured out how to add apps to login items and turn on password for screen saver and sleep. Now I still need to change the clock to 24h mode and make finder display local hard drives and network mounts on the desktop.
I need to do this either with applescript (this is preferred) or alternatively with bash script if applescript for some reason doesn't work here.

Can somebody help with this?