found my own answer
Shortly after posting, I discovered that Live Chat was "on"

at Apple, so I went on.
I post the answer received, which worked to solve my problem, and hopefully help other readers.

Hi, my name is Greg. Welcome to Apple!
Greg: Hello, I'm looking over the information you just provided.
TreeTreeTree: Hi Greg, thank you. I am having problems syncing my address book to my '.Mac' account
Greg: What happens when you attempt to sync?
TreeTreeTree: syncing has produced multiple duplicate entries in both local addy book and '.Mac' addy book
TreeTreeTree: I have cleaned the local by using "find duplicates" but the '.Mac' continues to grow with subsequent syncs
Greg: How many computers are you syncing?
TreeTreeTree: one... macbook pro 15"
TreeTreeTree: to continue my story, I finally purged my '.Mac' Address Book to empty, and attempted another sync
TreeTreeTree: I got the "% change" warning... cancelled sync, backed up local Address Book, and then continued sync
TreeTreeTree: the result was over 100 deletions from the local Address Book, and an empty '.Mac' Address Book
TreeTreeTree: so here I am. Stuck
Greg: ok so you will first need to restore the backup of the local address book
TreeTreeTree: restore is done
Greg: Try to reset your '.Mac' Sync data on the computer with the most current data.
Here's how to reset sync information:
1. Open System Preferences and click '.Mac'
2. Click Advanced and then click Reset Sync Data
3. Choose the information you want to reset from the Replace pop-up menu (such as Bookmarks, Contacts, or All Sync Info)
4. Click the right arrow. The screen will change to say "On '.Mac' with sync info from this computer,"
5. Click Replace. This will replace the information on '.Mac' with the information from your computer.
Greg: After resetting your sync information, you may need to reset your '.Mac' Address Book if you sync it. Here's how:
1. Go to '.Mac' http://www'.Mac'.com and log in.
2. Click Address Book and then click Preferences.
3. Deselect the "Turn on '.Mac''.Mac' Address Book Synchronization" checkbox and click Save.
4. Click Preferences again, reselect the checkbox, and click Save.
TreeTreeTree: big answer... reading.... can I copy and paste this conversation?
Greg: To copy your chat, click before the first word in the chat and drag your cursor to the bottom of the chat. Then copy and paste the text into a TextEdit, Pages, or Word document.
TreeTreeTree: ok thanks.
Greg: No problem
TreeTreeTree: trying steps... will you be able to continue in a few minutes?
Greg: sure
TreeTreeTree: thanks
Greg: Your welcome
TreeTreeTree: OK thanks... synced 306 cards in each
Greg: Excellent!
TreeTreeTree: now what did I do to generate the unwanted duplicates
Greg: I do not know what caused that. It should now be working though.
TreeTreeTree: >holding breath< thank you... I'll now have a clue to how to repair
Greg: Thank you for chatting with us. We value your feedback. Please click the blue "Close" button at top left to answer a few questions about your experience with us today.
TreeTreeTree: ok will do after I repaste the entire conversation
Greg was very patient as I worked through the problem and got good results. He did fail to tell me that the follow-up survey offers to email an entire transcript... but that is a small point.