If you can inspect the vehicle, you can look at the gear console. Quadra Drive II systems will state this right under the gear shift.
You can also stick your head under and look at the rear axle - if it has electronic connections going into it, it's QDII, as they are used to control the LSD.
I'm not sure if it still works, but it used to be if you used the following link (replacing the VIN at the end of the link), it would bring up the build sheet for your vehicle:
I am sure it is possible to decode the VIN by hand as well, but I am not sure what digit/code you are looking for.
With the above, you shouldn't have to ask the dealer anything, provided you can see it in person.