How can I upload and replace a Wordpress theme?

I just created my first Wordpress theme. I zipped it up and installed it on the server using the Wordpress 3.0.1 Administration Panel. That worked fine. But now I've made a few changes to my theme and I want to update it. I couldn't find an "upgrade" option for uploaded themes so I tried just uploading it again. This is开发者_StackOverflow what I got.

Installing Theme from uploaded file: my-theme.zip

Unpacking the package…

Installing the theme…

Destination folder already exists. /path/to/wordpress/wp-content/themes/my-theme/

Theme install failed.

Is there any way to update the theme through the administration panel? Or do I have to access the filesystem somehow (FTP, etc.) and delete the directory first?

---

You can do it all through the control panel. Each theme has a Delete link that you can use to wipe it from the server's file system. Once it's gone, you can re-intall your updated version.