I did it in a day. Really taking my time to make sure there were no wrinkles. I can't remember exactly why since it's been awhile but I think the seats do have to come out..
You'll need hog rings and hog ring pliers too. I have plenty left if you get in a pinch..
This video is a decent overview:
http://www.youtube.com/watch?v=AGDQC-8byGw