MadPyro,
it's a lot about coding. But, you don't have to start from scratch. If you search your harddrive, you will find a file called classic.jar. This is the default FF theme in a renamed zip file. You can take the file, make a copy of it in a working folder on your harddrive, and rename the copy to classic.zip. Now, unzip that file and it will create the directory structure that is required. You can then look thru those folders and see the image files required.
Now, before you try to create a new a new jar file from the files you modify, there are a couple of file you will have to create. They are: the install.rdf and contents.rdf. These files tell FF the details about your skin. Additionally, you'll need to obtain a GUID for your skin...you can get this from the mozilla IRC server.
Here's some helpful links...
Link to install.rdf and contents.rdf instructions: http://www.mozilla.org/projects/firefox/extensions/packaging/themes.html
Link to mozilla GUID Generation information:
http://kb.mozillazine.org/Install.rdf
Additionally, you may want to download a couple of the themes that are already out there, and unzip the .jar file to look at the structure other developers have used.
Good luck.
Wicked.