Seems like you should be able to undo what ever you done in Terminal some how. Maybe some kind of "sudo apt-get remove" or some such. I thought about 13.04 but liked the long term support of 12.04 and went with it instead of the "latest greatest" version and I'm glad I did. I'm sure someone will have an answer for ya' shortly. You might even want to repost it over in the Install area of the forum too.