2004 Passenger Side Mirror Housing

[Blinky316]

I've got a 2004 Limited and this morning the plastic housing (shell) on my passenger side mirror took a hit from a tree branch, resulting in a hole about the size of a quarter. My question is can I pop off that shell and replace it or do I need to replace the whole mirror unit? Also is it possible to buy just that part or do I need to buy the whole unit and just swap the plastic piece. Any advice or information is welcome. Thanks for the help.