Several options:
• Create your own door
• If you're lucky the door you like exports with separated groups. This would make separating front and back a lot easier. See the How-To listed below.
• If you're not that lucky you need something like Blender to separate the front and back materials.
• This thread explains how to add deformations (opening the door)

Here is a How-To to change material names:
https://dodecagon.nl/Docs/ChangeMateria ... _Names.pdf
https://dodecagon.nl/Docs/ChangeMateria ... _files.zip