The theme I want to use for my blog has static sidebars. Now I'm looking for the way to make both sidebars dynamic, so widgets can be added/removed from the 'Widgets' page inside the WP admin panel. Can someone direct me to the info I need? (Or if you can do it for me, please let me know)
Sounds like you are talking about how to make them look good like that ? It's a matter of using the right images. That's graphic work, it has nothing to do with how the sidebars are set up. You can access your sidebars from your Dashboard->Appearance->Widgets and then put the code for your images or graphics in text widgets. Is this what you meant ?
That's where my problem is: when I add widgets in the widgets admin panel, nothing happens - the default widgets are not replaced, nor are any widgets added. That's why I assume the sidebars are controlled by what's in the sidebar.php template files - now I'm looking for a change that allows me to add/remove/rearrange the widgets from the widgets panel in the WP admin area...
Here is a nice tutorial about dynamic sidebars. http://www.balkhis.com/web-designs-resources/how-to-add-a-dynamic-sidebar-in-wordpress/
what version of wordpress are you running. If its the latest you can search wordpress for the dynamic sidebar plugin