For those working on it now, these are the steps to create a window with "Hello World" that disappears when you click an Ok button:
0. Backup your SavedVariables directory -- edit: not sure when but all my SavedVariables got reset in creating this mod and through a reload/log out and in
1. File->New Project, enter the name HelloWorld
2. fill out .toc info, save to AddOns\HelloWorld\HelloWorld.toc
3. right-click HelloWorld on the left in the Project Explorer
4. choose Add New Form, a form1.xml should appear in the tree
5. double-click form1.xml, you'll now see a bordered dialog
6. Select the dialog, then go to the properties tab
7. Change the Name attribute (under Design) from Form1 to HelloWorldFrame
6. From the toolbox on the right, select Label
8. While Label is selected, draw a rectangle covering a good amount of space in the upper half of the form.
9. Go to the properties tab (helps to undock for this and future steps)
10. Change the Text attribute to "Hello World"
11. From the toolbox, select Button
12. Draw a rectangle to be the button in the lower half of the form.
13. Go to the properties tab
14. Change the Text attribute to "Ok"
15. Click in the OnClick() box below
16. In the box enter: HelloWorldFrame:Hide()
17. Save
both the xml and the toc (the toc changed when you added the form)
Then log in to the game
Unfortunately tho first load is ok, when I ReloadUI() a ton of textures disappear/become green squares (action buttons, minimap buttons, etc). I'm going to see if I can move all the extracted files elsewhere and point wowuides to the other spot.