changing the association of a contact
First, export your contacts.  From the Contacts app, touch the menu button and select Import/Export.  Then choose to export to SD.  Then from the SD card, transfer the file to your computer (I used Dropbox).  At this point I simply deleted all the contacts off my phone.  I get an error notifications that sync had failed because too many contacts had been deleted, but when I tapped on it, it gave me the option to go ahead and delete them on Google.

Then I went to Google Contacts and imported all my contacts.  Then I did a bit of cleanup, and everything got synced back to my phone.