Yeah, if it's like a '91 126, open the roof about half way, and look along the front edge of the liner. You should see 4 white push-pins holding the liner up.
Use a small screwdriver or putty knife to pop them out. Then pull the liner out and up over the top of the roof to remove it. Once you get it out, you should be able to devise a way to make the fabric stay up.

DG