It is possible.
In fact, installation of the new grille is easy. Just maneuver it in through the opening in the bumper, align it with the opening and then pull towards yourself until the locking tabs click (pull around the perimeter to engage them all).
But removal of the old one can be a major PITA. It is held in place by locking tabs. Merely forcefully pushing the grille in might break the tabs, meaning that it is a better idea to disengage them as you push the old grille in. I don't remember which way these tabs should be moved to disengage, so you might need some sort of hook-shaped tool for that.
However, if your old grille is already broken and useless, you can just cut out the mesh area completely, thus gaining easy access to the inside. And then you should be able to easily disengage the tabs and remove the remaining "frame" portion of the old grille.
Last edited by AndreyT; 09-14-2012 at 04:09 PM.