I suppose it depends on the brand you buy, because I've never heard of having to remove anything. That sounds rather counterproductive, IMO. Regardless, I have and like the full length Maximum Motorsports ones. The main thing about buying subs is that you get weld in, not bolt in; and preferably full length, not standard length. They aren't an expensive enough part to be worth going cheap on, just get good ones and have it done right so you won't be sorry later. I wouldn't say it's difficult, but it is involved. You'll want somebody who'se good with a torch doing it, and a good set will need to be welded in peice by peice so it's a bit time consuming- but it isn't rocket science. Something that should be done to every Mustang.