Ok, I was told by OWC that you can also update the firmware through Bootcamp, so that's good news.
EDIT: @mdgm: sorry, I just saw your post! Have you tried it before? So it's as easy as making a Bootcamp partition on my SSD and then installing the firmware from Bootcamp? And after that I can just remove the partition (since my SSD is only 120GB and I don't have the room to keep the partition)?