I have never used Word or Office, but I can at least tell you tools that I do know are in use on Linux. I have no idea how the compare.
A lot of people use LaTex plus BibTex, both markup languages that can output to MLA style papers. An easy-to-use front end for LaTex is Lyx
http://www.lyx.org/ (although I myself use Sphinx, which is not a GUI application but does output to LaTex).
I have no idea how that will compare to your old workflow of Office; probably it will be very different. But LaTex is widely used for MLA formatting in research papers published by the company for which I work.
Hope that helps.