from what I know you need skinstudio to make a windowblinds theme.
Skinstudio comes in various flavors, the free version will start you off nicely if you don't mind the 5-10 second wait until it opens (purchasing full version will remove the wait time, "nag" screen).
Skinstudio brakes down the sections that you can skin. Choose a starting place and spread out from there (some people like to start with the start button, others like to start with the window frame borders, others start with the task bar or task bar buttons, etc.).
I wouldn't know of any other place to start but to start with skinstudio. I didn't know you could create a windowblinds theme (.wba file) without it?! (maybe I'm wrong, wouldn't be the first time). You need windowblinds installed to apply the theme that you're editing. Windowblinds is available as a 60 day trial (at least I think it's still available as a 60 day trial).
hope that helps you with some of your questions.
