IIRC the rate code is Z34, good for 2 paid nights. The rate isn't the most competitive, so you are not really getting $100 off. The $100 credit is not valid on points or free night cert reservations.

If you were to do 2 paid nights, it may be worth your while to see if the hotel you are interested in is available through Amex FHR/THC or similar program from Chase/Capital One and compare the perks.