No lights on dash - are any of the other things still working?? (radio,
etc).
If the radio quits as well, it is probably power (ie from the battery)
related. It could be that you have a bad connection on the battery and
can be easily checked. Of course, if could also be beyond that point,
where it is going to the fusebox and is distributed through out the
car.

Many things could cause things like this -- I am frankly appalled by
the attitude of your dealer.

Remco