Trident window blind

Hi everyone,
I'm looking for advice on how to remove the window blind cassette from the rear near side window. I can see that to get at the screws that fix the cassette I'l have to remove the panels that conceal them but at the top there's A piece that I can only describe as an old fashioned pelmet concealing the curtain track and the top of the blind cassette. I can't see how this is connected to the van at all so any help on this topic will be much appreciated. If anyone has repaired a blind advice on that would be welcome as well. The problem is that a strip about 1.5 cm to 2 cm wide is torn at the edge and this will eventually detach itself all the way down the blind, I've thought of using some tin adhesive tape and then over stitching the repair as well.