An upgrade of such an install isn't really different from a normal
update. You have to upload the new files, run the install script in update mode and that's it. The only difference is that the files are probably in slightly different places.
Having said that and with reference to the recent
exploits, you may want to do a proper manual install anyway (you can keep your database, i.e. won't lose your stories, etc.) for your own safety ...
bye, Dirk