You shouldn't have to go too deep with the credit cards. If you are replacing the grill, just rip it out and don't worry about messing it up. Mine came out in pieces.
If you just need to remove it and replace it again, try banging on it a little bit to help "loosen" it up in case it has kind of "glued" itself around the periphery. Also, if you remove your NAV or radio, you can give it a push from that direction and it might help some.
2001 530i/5 (E39), Topaz Blue/Stone Green/Black (118k miles) *very rare interior/exterior color combo*
2005 545i/SMG (E60), ED Order, Titanium Grey/Grey (lease over)
2014 535d (F10), ED Order Summer 2014: THIS IS THE PLAN SO FAR