Sure it's an Excel question, how else are you going to do
massive updates. Start from the address book and export it,
being careful to get all of the fields, and watch
out for the comments. It did this 6 years ago.
I didn't have an address book then but I made up some entries
so that I could export and have the fields correct when I populated
it with data rearranged from AOL..
Then work with it in Excel. When you update your address book, you
will probably have to add a column with spaces in it all the way down
for your used range to generate a comma on end so that it can be
exported from Excel and imported back to the address book without
losing the last column.