I did this last week transferring my phone book from a 200LX to OG.
Check out the excellent article at http://www.cdpubs.com by John Blue
on transferring data from 95LX to OG.
This article gives you the structure of the OG phone book etc.
Using this as a basis open your 100LX phonebook in the 100LX database,
move data from the fields not in the OG phonebook structure to
fields in it or to the notes. Then use the Modify Database option
in the File menu to move the fields around and delete the extra
ones until they match the OG phonebook structure. Then transfer
the OG Phone book to the SRAM card, then use GDBIO and follow
the directions in the article above to merge your phonebook with
that on the SRAM card from the OG, put the new phonebook back on the
SRAM card in the same directory and with the same name, place it
in the OG and transfer the data from SRAM back to OG. I would advice
you to back up all the files used in the above before you try it.
I had no problems though. The one thing to note is that GDBIO can't
export the notes field so I had to rewrite these again in the OG
phonebook. Was a great way to practice Graffiti though :-)
Hope this helps!
William