Thanks for the quick reply!
And now the totally stupid question... I went to
Top Sony Forums > Downloads > Firmware > W910

Em... what are the R1CA029_RED52, R1CA031_RED52, R1CA037_RED52, etc...
If these are firmware version, how do I know if a version is compatible with my phone? Are all the versions compatible???

And moreover I didn't understand - Can I just update the firmware and get greek language support, without dealing with the .lng and .t9 files?

THANKS!