2004 Grand Cherokee's air conditioning defrost only

I have a 2004 Grand Cherokee's air conditioning works but seems to be stuck in the defrost mode. Air blows out of the defroster vents only, regardless of the switch setting.

I assume that the switch is bad. If so how do I get to it without damaging the dash? What is the secret to getting behind the panel?

Could it be something else?

Thanks

Gary