I'd like to upgrade the factory subwoofer that came w/ my 04 Explorer w/ the CD-6 HU, but I have some questions that I hope you guys can help me with.

1) Is the factory sub self-powered or is there a separate amp?

2) How big is the sub?

3) What's the easiest way to remove the bugger?

4) Are there any drop in replacements?

Thanks!