Edit Benchmark files

Hi everybody:

I've downloaded both the BMW & Classroom benchmark files from Blender's website.
What I'd like to do is to edit them, but when I select one of the chairs in the Classroom file to edit it, I can't see the mesh. I just see a plane selected & that's all.
Is there a way to edit them (as well as other parts of that file) or it's protected?

Thank you.
Marcelo.