I have just finished a thorough search of all the gcd FW files back to version 4.10 and there is no mention of the language guide. I found a warning at the same time stating not to use a lower FW version that 4 as it causes the screen to fail.
Garmin support were no more helpful than a piece of toast to a deep sea diver, so I think it's time to give up and put a translator on my Android instead.