If you want to really customize Ubuntu and you don't want it to be a total pain in the butt, you're going to need to enable the configuration editor. Here's how to do it (at least it worked in Gnome).

- Right-click on the main menu choose "Edit Menus".

- In the left-hand pane, click the expansion arrow next to "Applications" and then choose "System Tools".

- In the right-hand pane, check the box next to "Configuration Editor" and then choose the "Close" button.

Once this is done you can then run the Configuration Editor by going to "Applications" -> "System Tools" -> "Configuration Editor" in the menu bar.