Forza Texture Tool 1.1
Signing key changed, Auth.key / XBE patch no longer necessary for use of this tool.

This is a very basic texture extraction tool.  Given paintjobs from your
livery folder, it can convert the textures to DDS files, which can be
edited with Adobe Photoshop, given the right plugins (nVidia has a good
DDS plugin that can be used with Photoshop or Paint Shop Pro).

To use:
1) Copy over the paintjob from your xbox.  
   Paintjobs are located in the 'livery' folder under your user profile 
   folder, like so:
   You can find which folder contains your profile by inspecting the 
   "savemeta.xbx" file in each folder with a text editor until you find
   your profile name.
   Then, you need to find the proper paintjob under the livery folder.
   Unfortunately, each paintjob has a unique hashcode as well, and the
   only way to determine what paintjob is which is to either guess by
   creation date, or copy over each paintjob and unpack (see below) until
   you find what you are looking for.
   The paintjob will consist of 4 files:
2) Unpack / convert texture files.
   Select the base filename (directory and hashcode) of the paintjob you
   wish to work on by clicking the browse button next to the main textbox.
   Then, click unpack.  In the same directory as the paintjob, 3 files
   will be generated:
   <hashcode> - a 512x512 DXT5 in-game texture.
   <hashcode> - a 512x512 DXT5 damage map texture.
   <hashcode> - a 1024x1024 DXT5 texture used in the garage.
3) Pack / convert texture files back into original format.
   This will convert the dds files in the same folder with same names as
   above back into .texture files, and also pack them into the .pkg file
   for redistribution across system link and Xbox Live (online AuthKey 
   required).  The original texture files and package will be renamed as
   .old files in case of a problem.  If the hacked texture works fine, 
   these can be safely deleted.
There you have it!  Easy as 1, 2, 3!

Special thanks to MeanMF, who primarily coded the tool, and brienj for 
the basic file layout specifications.