I just popped out here to ask the exact same question - I have version 3.0.1. installed from a Fantastico installation and see that I need to jump to 3.0.5. The forum is new - there are no posts, BUT, I did modify a number of files in the /styles folder, added images, changed the stylesheet, etc.
Should I follow the same instructions provided here - download the full version, not the upgrade version -- and replace everything but the files/folders you suggested? I would presume, however, that I should also not upload/overwrite my /styles/ folder, or I will lose all of the changes to my design. Will it hurt my installation to not upload that folder?
Thanks in advance, and for answering rookie questions.