Hi Nico71,
I don't know if you have an editor for changing the menu_1024_768.ini
I use winmerge (freeware), easy to use, it can be used to compare 2 files and highlights all the differences.
http://winmerge.org/
You'll have to put the Realnav changes into the OLC GUI menu_1024_768.ini.
Make sure you have a back-up first.
Sorry I can't help you more.