shading on instances * solved *

So am trying to tweak the shading on a window in a castle model, and realized the particular window I want is actually an instance of another in the model. when I look at the surfaces tab for the window I'm intersted in I see nothing - if I adjust the shading on the "original" say dial the opacity down I see it affect the "instance"
2 questions - 1) is there a way to give the instance unique sdhading - i,e, it's own surface ?
and b) I want to make the window an emitter so I set it's (the original) emission color to yellow and added a map thats black except for the areas I want to emit light (which are white) but when I render the instance is completely invisible - as if I'd set the opacity to zero? Is this an instance issue - or a misunderstanding in how emissive surfaces work?
Thanks
Comments
If you want diffrent material properties then you can use a simple duplicate (which uses as much memory as the original) or a Geometry Shell (which saves on geometry memory but has its own materials) instead. Just select the instance, ctrl-c to copy its placement, then select the original and either Edit>Duplicate>Duplicate Node(s) or Create>New Geometry Shell, select the new item, and ctrl-v to paste its placement (and for the Geometry Shell also zero the push modifier offset).
Awesome - Thanks!
FYI - I needed to turn off thin-walled for the emission map to work.