Clearly we aren't following you so ANYTHING of visual content you can post or links to such TIS instructions would help us all out a lot. Is there anyone who has read this thread that is near you with an E39 who has need of replacing this cover? Perhaps you can avail your services for the good of Bimmerfest and take pictures of the replacement procedures!
However, one thing I'd like to point out is that this does not at all pertain to the REAR WINDOW rubber molding. My two upper corners of this rubber gasket/molding are simply gone, dried up, etc.
2001 530i/5 (E39), Topaz Blue/Stone Green/Black (118k miles) *very rare interior/exterior color combo*
2005 545i/SMG (E60), ED Order, Titanium Grey/Grey (lease over)
2014 535d (F10), ED Order Summer 2014: THIS IS THE PLAN SO FAR