This was one of my favorite projects to date. The tutorial I found here:
https://docs.google.com/View?id=dfhzndwh_3rszbxhn&pli=1 was really easy to follow, even though it was my first time to sew a zipper. I also looked at another tutorial on zippers here:
http://sewmamasew.com/blog2/2007/05/installing-a-zipper-tutorial-by-michelle/ just to get a little more info (I had to shorten my zipper). All the fabric pieces that you need are small, so it easy to use scraps and it only took me a few hours to make.
Rating: Easy (beginner). Time: 2-3 hours.