I would always recommend changing the appearance (branding) of the native/OOB controls over build new controls and trying to inherit their behavior, particularly in this case. There is a substantial amount of dynamic javascript that comes along for the ride with the "I Like It" and "Tags & Notes" buttons, so you're not going to easily replicate that with your own set of controls.
The only other approach is to brand what's already there. Without knowing exactly how your customer changed the buttons it's hard to know whether or not this approach would work and because of the way the buttons are rendered anything you come up with here is going to be a hack.
Can you share what the new buttons look like and maybe we can give you some guidance on how to alter what's already there?