Using nginx + wordpress with all wordpress files in a subdirectory

My Setup
I am running nginx 0.7.67 on Debian Lenny as a webserver, not as a reverse proxy. I am using php5-fpm to handle my PHP requests, which works fine.

My Aim
I would like to have a WordPress installation that is laid out as described here clean wordpress subversion installation. I would like to have a clean WordPress installation without cluttering my server root directory with all the WordPress files.
That means that my wordpress installation would be in /wordpress and my themes and plugins inside /wordpress-content.

The important point however is that if you navigate to my domain www.example.com then you would be taken directly to the WordPress blog, without having to specify the subdirectory where WordPress lives.

I found a how-to at the nginx site installing wordpress but unfortunately this is for moving the entire WordPress directory instead of redirecting the traffic to it.

I tried with the following configuration:
example.conf in sites-available

server {
  listen 80;
  server_name     www.example.com;
  access_log      /var/log/nginx/www.example.com.access.log main;
  root            /var/www/example/htdocs;

  location / {
     try_files $uri $uri/ /wordpress/index.php?q=$uri&$args;
  }


  include /etc/nginx/includes/php5-wordpress.conf;
  include /etc/nginx/includes/deny.conf;
}

php5-wordpress.conf in includes

location /wordpress {
   try_files $uri $uri/ /wordpress/index.php?q=$uri&$args;
}

location ~ \.php$ {
       fastcgi_split_path_info ^(/wordpress)(/.*)$;
       fastcgi_ignore_client_abort on;
       fastcgi_pass   unix:/var/run/php5-fpm.socket;
       fastcgi_index  index.php;
       include        /etc/nginx/fastcgi_params;
}

fastcgi_params

fastcgi_param  SCRIPT_FILENAME    $document_root$fastcgi_script_name;
fastcgi_param  QUERY_STRING       $query_string;
fastcgi_param  REQUEST_METHOD     $request_method;
fastcgi_param  CONTENT_TYPE       $content_type;
fastcgi_param  CONTENT_LENGTH     $content_length;

fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;
fastcgi_param  DOCUMENT_ROOT      $document_root;
fastcgi_param  SERVER_PROTOCOL    $server_protocol;

fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;

fastcgi_param  REMOTE_ADDR        $remote_addr;
fastcgi_param  REMOTE_PORT        $remote_port;
fastcgi_param  SERVER_ADDR        $server_addr;
fastcgi_param  SERVER_PORT        $server_port;
fastcgi_param  SERVER_NAME        $server_name;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fastcgi_param  REDIRECT_STATUS    200;

The problems I have is that when I go to the address "http://www.example.com" I get a 403 error as I disabled directory listing. Instead I would like my WordPress to appear then. Also if I navigate to "http://www.example.com/wordpress" I get a "file not found" error. However if I comment out the fastcgi_split_path_info line in my php5-wordpress.conf at least the WordPress installation works inside /wordpress.

I need help how to debug this behavior or where I can find more information.

Update: Added error log entry for the 403 error.

in the error.log I get the following entry for the 403 error:

2010/12/11 07:54:24 [error] 9496#0: *1 directory index of
"/var/www/example/htdocs/" is forbidden, client: XXX.XXX.XXX.XXX,
 server: www.example.com, request: "GET / HTTP/1.1", host: "www.example.com"

Update 2: Added the nginx.conf below:

user www-data;
worker_processes  1;

error_log  /var/log/nginx/error.log;
pid        /var/run/nginx.pid;

events {
    worker_connections  1024;
}

http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format   main '$remote_addr - $remote_user [$time_local]  $status '
    '"$request" $body_bytes_sent "$http_referer" '
    '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;
    tcp_nodelay        on;

    gzip  on;

    index index.php index.html;

    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;
}