I have been myself in the original Volvo 480 Sunroof nightmare for the last year and a half.
The thing is surely screwed, not glued to the roof. Screws can only be seen when you remove the roof upholstery. I do recall aswell there are some metal parts sodered to the roof sheet.
Our Volvo 480 spanish Club administrator is going right now or has plans to transplant a complete roof sheet with it's sunroof into one of his cars. He his planning also to cut right on top of all pillars I think. I could ask him to share his experience this far.
The mechanism is a poor design. First of all you need to make sure that the "endless thread" (nº 16 on the image) that connects the motor with the lifting mechanism itself is both sides well aligned, otherwise if one side pushes harder that the other it will break one after another the damm "coupling piece" (part 15 on the image). I had to get me an entire oringinal one I found in german ebay, take this "endless thread" and most of the other lifting parts and do the transplant. Then made silicon molds of the coupling piece to get poliethilene replicas. The mechanism kept breaking piece after piece. I had then nylon 618 replicas made by some 3D printing guys. And is holding on this far.....finally !!
So my advice is to try an aftermaket one. It may be more expensive or a titanic implant on the car, but you'll get a working, even sliding roof!