There are ways to theme your device, to an extent, without manually editing/replacing files and/or rooting your device, but they aren't nearly as extensive or customizable. You can download new home launchers like Launcher Pro, but that only does so much.
The files, "framework-res.apk," and, "services.jar," are really only accessible if you root your device. They need to be edited/replaced in order to customize the notification bar and apply certain themes or modifications/customizations. I believe there's a way to replace them via ADB without root, but you can only do that. You can't pull it from your device, edit it, and put it back. From what I've read, you can only push a new file to the same directory and replace the original in the process. If you're on 2.1, then all you need to do is root. If you're on 2.2, then you need to root your phone and deodex it.
Honestly though, rooting your device while running Froyo isn't that difficult, tedious, or risky. It's even easier if you're still on 2.1. If you're on 2.2, however, you will need to deodex your device before you can do things like apply custom themes or notification bar customizations, which does technically involve some risk. You can recover from a failed deodex, but it the process of deodexing or recovering from a failed one can be tricky sometimes.
