Well you don't remove it since its an integral part of the OS. To turn it off, just turn off web sharing from your preference panel.
Xampp is more for developement than as a production server. In leopard you have Apache 2 something and PHP 5 I believe, you will most likely have to access it through Darwin. In fact it is easier than putting Xampp on your computer. Setting up MySql and phpmyadmin isn't to big a deal for the production side. Don't get me wrong here - Xampp is most excellant for developement.
If you uninstall Xampp, you should be able to just do a simple re-install in your applications folder. Unless you altered the Apple preinstalled version of Apache's config or ini, you needent worry about it. If you managed to, just replace the files with the .bak files. All files with the Xampp configuration were removed when you uninstalled it.
If I misunderstood your comment, try again.