For the moment I write my documents using mostly Writer and Math. Is it possible to export those documents to the LaTeX format? Or do I have to rewrite everything from scratch in a dedicated program?
installing writer2latex is probably your best bet
http://extensions.libreoffice.org/extension-center/writer2latex-1
This might help with writing as well
http://extensions.libreoffice.org/extension-center/texmaths-1
can’t vouch for either as I am not a latex user (have only played around with it a little)