Drop table, delete options, deactivate plugin

Hey! I’m working on a plugin that creates a table and sets some options. When you deactivate the plugin via ‘site admin -> plugins’ I’m fine with it leaving the table in the database but I want to at least provide the possibility of completly uninstalling the plugin, meaning dropping the table, deleting the options and deactivating the plugin.
I set up an options page with a link to uninstall the plugin. It calls the following function that I copied from another plugin. It doesn’t seem to work right and I have problems understanding the code (by the way, where do I find some kind of developer documentation? I would help if it isn’t set up already but I think it’s a very important thing to have. The one here on the site, is that the one? Not complete at all, isn’t it?).

This is the function that’s supposed to uninstall the plugin:

function myplugin_plugin_uninstall() {
global $table_prefix, $user_level;
if ( $user_level >= 10 ) {
// Drop MySQL Tables
$SQL = "DROP TABLE ".$table_prefix."myplugin";
mysql_query($SQL) or die("An unexpected error occured.".mysql_error());
// Delete Option
delete_option('myplugin_config');
// Deactivate Plugin
$current = get_settings('active_plugins');
array_splice($current, array_search("myplugin.php", $current), 1 );
update_option('active_plugins', $current);
$redirect_url = wp_nonce_url("plugins.php?action=deactivate&plugin=myplugin.php", 'deactivate-plugin_myplugin.php');
header('Location: '.$redirect_url);
die();
}
}

What is e.g. wp_nonce_url?

When I click the uninstall button on my options page a site loads aksing me, if I really wanna deactivate the plugin named “”. I click yes and another page loads asking me if I want to really deactivate the plugin named “myplugin”. I click yes and the plugin deactivated but neither the table is dropped nor the options deleted. What am I doing? What am I doing wrong?

Thanks alot for you help!! I hope this is the right place to post this, if not, where?