Firefox sidebar help needed

I'd like to try making a Firefox sidebar that holds a hierarchical menu of tags, where clicking on a tag in the sidebar sticks it in the appropriate tag input box on the diary entry page.

Mozilla has a "Creating an Empty Sidebar" page on its support wiki, but that's outdated (v1.0). I'm running 2.0 and most everybody else is running 1.5.

Are there any Firefox extension jocks out there that can help me out? I'd like just a basic empty sidebar; I think I can code up the innards that fills it up and talks to the main window, but that first step is the hardest.

Thanks.