Well, I did it with American fabric (inexpensive), but if I had cared more about the car I would have redone it with the expensive German stuff before reinstalling the board. This is the type of task that I would have to practice a few times before doing it well. I think many other people would be in the same boat. The problem is, removing fabric and cleaning the adhesive off the board is a project in itself, and I had neither the time nor the patience to do it more than once.
My experience is documented here:
http://www.peachparts.com/shopforum/detailing-interior/305919-sagging-headliner-can-re-foamed.html
A search for "headliner" or "seatcovers" or "upholstery" in the Detailing and Interior forum will probably yield a lot of useful information.
btw, I consider a sagging headliner in the back of the car to be a safety issue. But if you just tear the fabric off I suspect you would have crumbling foam falling into your eyes, which would be worse, I think.