Adding Setup Interface to XPI install

I want to add setup and configuration during installation of my mozilla 
toolbar extension.  I wrote a nice little XUL wizard application that 
accumulates and persists user information that will be used by my 
browser extension.  I need to run this setup app during my extension 
install but am not sure how to do so.  The Install object does include 
an execute method, but it expects an executable and my setup app is a 
XUL app.  Doesn't look like I can run the XUL setup app until after the 
chrome is updated and the browser is restarted.

Is there any way to run a XUL setup app during XPInstall of a browser 
extension without actually installing the setup app itself and 
restarting the browser?

Or maybe a way of having the mozilla browsers spawn the setup 
application at restart?

Barring that is there a way to add a UI to setup that
allows the setup to accumulate user info prior to performing the 
extension install?

Thanks,
David