Does anyone know of a way in 2012 to override the graphic of an individual element in a linked file?

I can tab through to select individual elements, but I can only change elements by category.

My situation is we have two tower files linked into the podium file. It is the podium file that we have our sheet set in.
I'm working on a scissor stair section, and between the runs of the stairs we have a wall. I want to be able to make this wall transparent so I can use the linework tool to show the stairs beyond as hidden lines. I don't want to make all walls from the linked file transparent, ant I don't want to hide the wall in question from the view and draw in the edges.

any suggestions would be great.

I beginning to realize that linked files are the bane of my existence, and will likely avoid them like the plague from now on.