Move from syncing contacts with Mac to Google

I am currently syncing my Contacts on my iPhone with my Mac, when I physically connect the two. I sync all my contacts on OS X with my Google account, and I already sync my calendars on my iPhone with my Google account. I would like to move to syncing my iPhone Contacts directly with Google. My main concern is all contacts being "reset" or something similar when I turn on G syncing on the phone and then quit syncing via iTunes. Anyone have any first-hand experience with this and can reassure me nothing bad will happen? 🙂 Or is there another preferred way to transition? Thanks for any input.