I'm afraid I don't know how the message output is made in the code.

But there is a couple of other things to try to search in the firmware.
At first, there are the references to the current FW version. For eTrex firmware version 2.80, the version WORD is located at 0x807d904e. I could only find the following refs to the version:
Code:
Please Login or Register to see the links
Near the latest offset, there's also ANSI string "&updt_lock_smphr", which is rather interesting.

Another option to try is to locate the "GUPDATE" strings. Again, there are only several strings in the firmware:
Code:
Please Login or Register to see the links