John,
The side walls I insulated first. Then I put in insulation in the top as well as the vapor barrier insulation as I was going to be heating this one all the time.
What I do when I buy these is at Menards they have a computer program that you can design whatever building you want. Then it prints out whatever materials you need from there. So it isn't really a kit. All the specialty work you have to figure on your own, like heating, plumbing, electrical, and concrete.