It's actually a vacuum actuator (you have 4). changeProbably the toughest one to change but if you're not afraid of a little work go for it. If you are get a hacksaw blade.

 

if its the damper then you can access it thru the floor vent itself.
remove the lower center console...then remove the plastic divert-er for the floor vent...it just pops out...then you should be able to get your hand up inside there and swap it out....i actually cut some holes and learned of this method to late.
if you search around there is a more descriptive write up somewhere.

 

Right behind the kick panel in the center on mine there is a little metal switch that goes back and forth. It switches floor on and off. Take the kick panel off and youll see it.

 

If you have a hand held vacuum pump like a Mity-Vac you can test the actuators individually and the whole system at once. Invaluable tool.

 

Just have to test them> A hand held vacuum source like a Mity-Vac works great for this.