Yves,
I am very grateful for your help! This worked beautifully once I found the correct directory to add the updated XSL spreadsheet into. It is different from my Windows 7 machine. On my Surface (which uses Windows RT) I have to put it into the following
directory:
C:\Users\user_name\AppData\Roaming\Microsoft\Bibliography\Style
Only this directory would work. I'm not sure what the others are for, especially since they have copies of the default XSL sheets in them. In any case, this worked, and I am a very happy Word 2013 user. This was the only major limitation I was facing
on my Surface RT.
Thanks again, a hundred times over.