I want to replace Libreoffice with Openoffice.org o Ubuntu 12.10 with GNOME Classic.But i want to install the italian version because I'm italian.
It is possible.
First, you would need to remove LibreOffice:
Then, you need to download Apache OpenOffice from their website: http://www.openoffice.org/download/other.html.
Download the Italian "full installation set" for Linux Intel DEB or Linux x86-64 DEB if you are running Ubuntu 64-bit.
Then, follow the installation instructions. In short:
Now, why install OpenOffice when you can perfectly install LibreOffice 4.0, and doing it from the PPA would make your life easier (automatic upgrades instead of repeating the process above over and over).
More importantly, if you look around the internet, you'll find most people recommending LibreOffice over OpenOffice for several reasons.