Upgrade ownCloud from manual install to repository

I started out with a manual installation on version 4.5.4. It was located in a /home/ folder rather than the /var/www/ directory, which gave me opportunity to think some more. So, let's begin.
Go to the folder your ownCloud installation is in and tar it, in case anything goes wrong.

sudo tar -cjvf owncloud.tar.bz2 owncloud/

Since it's now owned by root because of the sudo, make it yours now.

sudo chown orangensaft:orangensaft owncloud.tar.bz2

Subscribe to the new ownCloud server repository.

sudo vim /etc/apt/sources.list

Add this line at the bottom:

deb http://download.opensuse.org/repositories/isv:ownCloud:community/Debian_6.0/ /

Then add the key, update your repositories and install owncloud.

wget http://download.opensuse.org/repositories/isv:ownCloud:community/Debian_6.0/Release.key
sudo apt-key add - < Release.key
rm Release.key
sudo apt-get update && sudo apt-get install owncloud

If your manual ownCloud installation was not in /var/www/owncloud, you need to copy the config file to the new directory.

sudo cp config.php /var/www/owncloud/config/config.php

This is a step I didn't have to do: Copy your owncloud/data/ folder! This folder stores all your cloud files! Since I have it configured to a different mount (my /storage/), I was able to skip this.
Check your httpd config - in my case it's Apache: /etc/apache2/sites-available/ - and replace the old path with the new /var/www/owncloud/.
After you've done this, restart your httpd (sudo service apache2 restart) and you're done.
You should now be on version 4.5.7. :)