Hit Temperature Up until the unit says OFF (or just unplug the whole fridge, but it's going to be dark). Clear off the top shelves and remove them. Pop off the plastic cover-grate thing with a flathead screwdriver (jam it in from the bottom). Remove the two newly exposed screws. Slide the plastic cover forward, then slide the styrofoam assembly forward as well, exposing the damper unit. Unplug the cables right above it. Using your fingers (or the flathead from earlier) push the locking tabs on the left/right side of the unit until you can pop it out/tilt it forward, then wiggle it out. Slide the new unit in in reverse, then plug it back in. Do all the other steps in reverse, finishing with returning your temperature to 38/whatever you had it on. Wash off those top shelves, because I sure have been neglecting to do so.
Walk by your fridge and notice the lack of rattling!