It is neither quick nor easy to replace the material, especially if the car has a sunroof. I've done it, and it takes all day. Well worth it though, as compared to the $5-600 usually charged by an upholstery shop.

If the material you have is the original, there will be a layer of crumbling yellow/brown foam between the fabric and the backing board. This is what prevents simply gluing the material back up. If the fabric has already been replaced once (or more) this may no longer be present, and regluing might work.

I would not recommend using staples, as the kids might pull them out and get hold of them, and they tend to damage the backing board, making eventual replacement of the fabric more difficult.

If you have any further questions about the replacement process, I will be glad to answer them. The relevant section of the FAQ has a good description of the procedure. IPD also has one on their website.