Install Quantum GIS Desktop Ubuntu 12.10

You can use ubuntugis ppa, which contains everything you need:

 $ sudo apt-add-repository ppa:ubuntugis/ubuntugis-unstable
 $ sudo apt-get update
 $ sudo apt-get install qgis

The system will take after the necessary dependencies

Your problem also suggests that you have broken dependencies for qgis. One way to fix this is to clean your cache by running in terminal (you can open the terminal with alt + ctrl + T)

$ sudo apt-get clean

or

$ sudo apt-get autoclean

and then ask apt to try and correct any broken dependencies:

$ sudo apt-get -f install 

if the output is similar to :

$ 0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.

it means that you need some extra packages that you weren't informed about. To install them run:

$ sudo apt-get dist-upgrade