If I have understood you correctly, you want to open a div with change password link click, which contains the update password controls.
The best way is to use a jQuery overlay - which behaves like a modal window and when open, the outer region gets darkened.
To know more about Jquery Overlay, follow the links below,
Modal Popup Overlay[
^]
http://alvarojunior.com/jquery/joverlay/0.7.1/[
^]
http://jquerytools.org/documentation/overlay/index.html[
^]
Hope this will be a good start for you.
cheers