The dash vent is held in place by 2 tabs. Use 2 small flat screwdrivers to release them. The tabs are under the bottom of the vent, you should be able to feel them with the end of the screwdrivers. Both must be released at the same time. Once they are released, tilt the bottom of the vent towards the rear of the car to release the top.
GM service bulletin 04098A dated January 2006 describes the hazard switch replacement procedure. PM an email address and I'll send it to you, or maybe your dealer will let you have a copy.