I am about to take delivery of my new GMC 2500HD Crewcab. Does the Duramax engine require any special break in treatment - specifically can I begin to tow immediately with this truck or does it need some sort of break in before I put the engine under any kind of load?

Look in th owner manual. Drive a thousand miles or so before towing

I saw break them it like you are going to run them. But thats just my opinion.