I recently installed Alpine 630 changer in my 01 Disco II. I bought the changer and blitz adapter as a set online (I can't remember the name of the online store, and will post later once I get home) for $237 including shipping and handling. If you already have the connection port under your passenger seat, you may not need the blitz adapter (again, I'm not sure). My Disco is a SD7 and it did not have anything that resembled the changer connector, so I purchased the set.
Installation was a breeze once you get the stereo out. I tried with a metal piece for about 5 minutes and realized that taking out the stereo was not my forte. Took my Disco down to a local stereo shop and the guy there took something like 60 seconds with a couple of 'keys' to pop the stereo. From there, it was a super smooth install, although pushing the stereo back in with the somewhat bulky blitz adapter took some wiggling. FYI, I opted to leave my changer in my glove compartment unattached for convenience purpose, and I'm very happy. I will let you know the name of the vendor once I get home and find my invoice.
Update: The name of the vendor is
www.autotoys.com