The CSS editing upgrade is not recommended for purchase to those who do not have CSS editing experience and who cannot work independently. In the CSS Customization forum you will find links to CSS tutorials. We do have a volunteer, devblog who will help when time allows. he requests that those who ask for his help read this post http://csswiz.wordpress.com/2009/10/15/if-you-have-the-wp-com-css-upgrade/ The situation is that you must wait for him to find this thread when he logs in.
Also, I'm using a Firefox 3.5.7 browser and I do not see any lines in your sidebar at all. If you intend to edit CSS you will need to download two Firefox add-ons (Web Developer and Firebug).