Sorry for the delayed reply. Busy day today.
So, with FI03 on your phone, you're not going to be able to install an official OTA update, so at some point you're going to have to do a manual flash if you want the latest software version on your phone. The question is whether to do it now, or when an official update is pushed out and it's packaged up as a flashable TAR file.
I would probably recommend you flash the FH13 version now, via the "NO DATA" version of the easy to use Odin One-Click package. It looks like we should be seeing an official FI27 update soon, and this way, you'll be able to download this update OTA and install it. Flashing the FH13 TAR package will root your phone, but installing a future official update will remove root, as long as you don't use root to uninstall any system applications or mess with any other system files. It's possible that the previous owner did mess with some system applications, so if you want to be extra careful to avoid any future issues, you may want to use the "FULL SYSTEM RESTORE" version of the Odin One-Click file. This will wipe and restore you data partition as well, and put your phone back to factory status (except with root privileges).
Here is the post with instructions on what to do:
http://forums.androidcentral.com/ep...latest-method-fh13-ics-official-firmware.html