Hi IvanJJill,
to reinstall wordpress just go Dashboard -> Updates
In the first section where you can find:
"You have the latest version of WordPress. Future security updates will be applied automatically."
Click "Re-install Now"
If you've lost localization in Italian, you can force Wordpress to recognize the language by editing wp-config.php as described here:
http://codex.wordpress.org/Installing_WordPress_in_Your_Language
And then you should find in the above mentioned section the possibility to reinstall wordpress 3.8.1 automatically in your localized version!