Michael, believe me, I was as concerned as you are. It really is an easy fix and I cannot figure how this would void your warranty. All you have to do is pull of the trim piece on either side and re-tape the entire surface area beneath. All GM did was put one 2-2 1/2 inch piece of trape under the trim piece. You are simply going to add a 20" x 3" piece beneath the trim.
My dealer wanted to use window sealant on the entire area to cease the noise. Thankfully, Chief, Sadurbin and a few others gave me the needed support and encouragement to do this myself. Like I said, I was concerned about what I may be doing. The 3M tape cost me $5 and the whole job, going slowly and carefully, took no more than 30-45 minutes.
Be brave and do it yourself. A very easy job and I would even be willing to give you my phone number if you needed to call me during your installation if you need additional assistance. There are no "proper" tools. Just a #2 phillips regular and short (for the screw nearest the hinge). A grease pencil or white-board marker also help in marking the glass.
Jamie
PS. Since you're an owner, why not register here as it's free and loaded with great information and helpful tips.