OK, I solved it after poking around. For others who might be interested, here's what I did:
In the phpmyadmin interface, I selected the contacts table from the older version and exported it to an sql file. Then I imported it, but I made one small change to one line of the exported file. I changed:
INSERT INTO `contacts` (`contact_id`, `changed`, `del`, `name`, `email`, `firstname`, `surname`, `vcard`, `user_id`) VALUES
To:
INSERT IGNORE INTO `contacts` (`contact_id`, `changed`, `del`, `name`, `email`, `firstname`, `surname`, `vcard`, `user_id`) VALUES
I just added that one word "IGNORE". That way, when I selected the new table and chose 'import,' mysql did not complain about duplicate entries from the exported file (which did happen without the IGNORE.)
Anyway, it seemed straightforward enough.
Ross