I don't believe you'll earn Marriott points booking through 3rd party websites. However, if the rate on Marriott.com is higher than $79, you can always book the higher rate directly, then file for their Best Price Guarantee program (Look no Further) against getaroom's lower price. If successful, Marriott will not only match the $79 rate, but further discount by another 25% AND you'll earn Marriott points since your booking is directly with them vs. a third party.

Good luck....