In my experience, it's better to send things back directly than deal with 3rd parties. I used a service through ebay when my old 360 red ringed, they all sound like they have great deals and offers - 1/2/3 month warranty etc but more often than not they will break again a couple of days past the warranty. Mine did.
At least if you send it back to Microsoft you know 100% that it will be fine, you'll likely get a new console altogether.