Hi Csenger,
Unfortunately I can't program in any language, yet, because in this
year I'll go to university and learn it. 
Y'don't need no fancy university to learn coding! Go search "learn C++" or "C++ tutorial" and get started
I've never learned programming formally... which explains why I'm not great at it!... but really I think learning by doing is better than learning in a class. And that's more true for programming than almost anything else because All the tools and resources and peers and mentors you could need are right at your fingertips.
I'm particularly enjoying exploring the LibreOffice codebase 'cause they've got an OpenGrok set up, as well as Doxygen. Have a look around (I've linked to what I'm looking at currently):
http://opengrok.libreoffice.org/xref/writer/sw/source/ui/index/toxmgr.cxx#UpdateOrInsertTOX
http://docs.libreoffice.org/sw/html/classSwSection.html
Yesterday I set up Cscope so I can get those kinds of benefits directly from Vim (http://cscope.sourceforge.net/)
Seriously, jump in. It'll put you five steps ahead for your upcoming formal studies Plus it's Fun, damnit 
I thought a new GUI wouldn't be too hard to create, because no change
would be in functionality, it just looks otherwise.
That's would be the ideal
Depends how well the code is structured though. I know for instance the designers of Ardour pride themselves on the fact that the GUI is completely separable from the backend engines. I just wouldn't take it for granted, especially with something of the size and complexity of LO.
I hope someone will be willing to help me in this project.
And I'm asking those who don't like the ribbon to be open-minded,
because this is (or would be) the power of open-source
Well, code is law after all. Fastest way to be listened to is make a proof of concept. See over-optimistic encouragement above 
-r