Retrofitting DSP into a non-DSP vehicle has been done before. See
http://www.xoutpost.com/articles.php?...icle&artid=160 for one such example. To get this to work you will need, at a minimum, the DSP amp and wiring harness.
Personally, since the dealer screwed up and gave you bad info, I would take the parts back and ask for my money back.