Couldnt have said it better myself!
Unzip the file in a pendrive or an iPod, in my case I've to boot from the DVD with the pendrive plugged in or otherwise it wont mount.
Then you just open the console an CD /Volumes/NAME_OF_YOUR_PENDRIVE/
Make sure your drive is unmounted before you leave Disk Utility as stated in the first post.
Sorry if you don't understand something, I'm trying to help but my english is bad.
Thanks for helpin