you can clone/ghost your drive. i suggest Macrium reflect http://www.macrium.com/reflectfree.aspx
you can clone the drive with this. what cloning does is, rather than just getting the viewable files its gets all files and the boot info, etc.
after using it you can just tell your computer to boot to the new drive and your done.
oh and yes you can boot from an external drive. it will be one of your boot options in the bios, make sure the drive is plugged in when you boot.