Here is the current link to Duke for the DVD.
http://www.dukevideo.com/products/3480.htm
I'm not an expert but aren't those pictures of touring cars on the box in the auction? Makes you wonder if it is a 'home made' version by someone who doesn't know a 956 from a M3!
To be certain of getting the real thing buy it direct from Duke.
I expect that everyone is familiar with another in-car video called "Sports In-Car Experience". The cover depicts a black long-tail Day Off F1 GTR and was issued in 1998. It's good, but not a patch on In-Car 956.