User Login Screen in Flash CS3

Hi,
I am a bit of a newbie when it comes to flash, but I have managed to muddle my way through so far. However I have come across a bit of a problem. I am trying to create a simple login page, once the user has logged in successfully they will be taken to another site which contains their photos.

I have created the login page already, it has a Username and password plus the Submit button. I guess 2 things need to happen here:

1. I would like to be able to access an xml document which contains the Username and Password in order to validate the details.

2. Upon successful validation, the user is directed to another page which contains their gallery, I guess I need to add a navigateToURL here in actionscript where the URL is passed from the XML file to the code (the URL needs to come from an the same XML file, if possible).

I am trying to design this site so I don't need to keep accessing the actionscript in flash to add user details and URL links.

Can anyone advise how I can do the above? Any advise and guidance is greatly appreciated.