what happened to you really blows, and i can empathize with your frustration. what can i say... s!%t happens and sometimes people get screwed!
you should, however, be honest with the dealer. it may decrease you trade-in value by $500-$1000, but your integrity will remain intact. there are far too many people out there already who think that $$ is more important than attributes like character, integrity, and doing the right thing... don't join that club man!!!!!
Z owners are the good guys!!!