It's not easy! I watched my buddy who's a body man wrestle with removing mine. It fought him the whole way. Basically, there are tabs with lips that snap into place in a few areas. There are some post-like tabs, too -- and chances are you're going to break at least one of those during the removal. And the real problem seems to be that it clips where it meets the mirror-side of the housing AND the front side, so it's tough to get both separated at first.
I think I'd try to get the mirror-side (the top back portion) of the piece away from the unfinished black plastic bezel first. I watched my buddy wedge some auto-specific plastic tools under the front portion first, and it really took some doing. That being said, it's tough to find a way in to the back/top portion first...
If you have the new piece ready to go on, your best bet is to study that and see where the tabs are that need releasing, then see if you can find some of those plastic tools to wedge in there.
