I just did the mod tonight, and it took me about two hours to complete.
The module is located under the base of the storage compartment of the console, and you need to disassemble the entire console to access it. Come prepared with some plastic pry tools, a grabber, flashlight, these sockets: 7mm, 8mm, and 7/32", some extensions, and some patience. There's another thread that has a link to a good partial disassembly instruction manual, but you'll need to completely remove the side and back panels, and unbolt the main bracket assembly to access the module. Note that the rear panel is bolted to the sides with two 7/32" bolts at the top that are hidden by the rear cupholders, so you need to remove them as well.
The mod works perfectly, but I can only access it through the voice command. The plus side is that I have full display control on my iPhone, so I don't need to mess with Sync's kludgy menu system to access my music!