Or you could go that route as well. All of the instructions are included with that and they even have vehicle specific installation instructions. Be careful though, if you have the DIN style mounting, you won't need any special mounting kits. You might need antenna adaptors, but I'm not sure on the North American spec E38's. My Jap spec E32 didn't need an adaptor with my aftermarket Alpine deck, so your's might not. But check this before hand.
Post pics of the before and afters! Let us know how it looks!