SkunkWorks requires Decal version 18.104.22.168 or higher. See the Decal homepage for information on downloading and installing Decal.
It also requires Microsoft Windows Script version 5.6 or better. Get it here.
You will also need MSXML 4.0 SP2, which you can download here.
Windows 2000 or XP is required. Win9X/Me is no longer supported.
A Visual Basic 6.0 development environment will come in handy, but is not strictly required. SkunkWorks is written almost entirely in Visual Basic (I had to resort to C++ for the script hosting code), and the complete source is included in the installation. If something breaks on patch day, a VB compiler will put you in a better position to get up and running again quickly.