Of course if the adding of the repository failed, the next step will fail too. What the line:
"sudo wget http://www.medibuntu.org/sources.list.d/feisty.list -O /etc/apt/sources.list.d/medibuntu.list"
Is supposed to do is to get a text file and append it to /etc/apt/sources.list.d/medibuntu.list
You can do that yourself. Just go to that link - it will open in firefox, and copy and paste the text to a text editor (that you started as root: type "gksu gedit") And save it to that location. you will have to create the file medibuntu.list.

But -O is definitely not an invalid option for wget. Did you type this instead of just doing ctrl-c ctrl-v? -0 (zero) IS an invalid option.