Actually, I also updated with SEUS and my phone's CID has been changed to 53 as well (and i have a w580i). I believe you can use the FAR Manager plug in JDFlasher to view you files as in FSX, but I'm not sure how to upload.
Right now, I've been told that there is no free way to flash it to a lower CID number, so just keep waiting and you'll probably get a solution sooner or later.
(I'm waiting, too)