There are plugins to change the backend. Some of them get rid of all the (annoying) boxes you get when you log into the administration area, others allow you to theme the backend with your logo and your own login screen. Some of them allow you to control the menu on the left, removing items if you wish. I don't like many of those but you may want to search in wordpress.org for plugins for admin.
Now, to be an editor or have different roles, I would suggest the "members" plugin. It comes with 5 different roles that you can apply: subscriber, editor, contributor, author and administrator