Changed wordpress directory, but regretted

Dear Support

I am a total newbie in the web world and also in wordpress. Today I was editing bits and pieces on my new blog, and foolishly changed the wordpress directory and site directory under general settings i changed them both to spisdinaltan.dk, and then i got the error message. I have now logged in to the support site for Giving WordPress Its Own Directory but i dont understand most of it.
Therefore my question is :
1) can i undo the change of directories, i cant log in?
2) if I am to fix the problem where should I start?

Help I dont have a clue