I did the crossover upgrade to my LS-9's, and it was not difficult. Danny sells an upgrade kit for them that includes all the caps, instructions, and pictures telling how to do the upgrade. It made a nice improvement in the sound of an already great speaker. I also added the poly-fill too. I did not think that was hard either. I did not disconnect the drivers. I got a soft towel and draped it in the hole so that it was covering the outside of the cabinet. I let the driver rest on the towle so it did not damage the finish, and stuffed the area behind the port. It took about an hour to do each speaker as I recall. If you are only going to do one uprade, I would do the crossover upgrade because it will give the most improvement.
Good luck,
Mark