Hi S Paull... I, too, had a neck dissection on the left side. They removed my jugular, plus a muscle that connects neck and shoulder, plus nerves, etc.
I agree wholeheartedly with Erik K above. Get your husband a referral for physical therapy ASAP. My ENT kind of blew this part off, and in the weeks that followed my surgery my left shoulder got worse and worse. I kept "guarding" it, rather than stretching it, and that just made it worse. When I finally went to see a PT, I could barely move it at all. It was just a dead limb.
In about three-four weeks time, though, I have seen a remarkable turnaround. My PT massages my neck and shoulder, stretches it out, then has me do basic range of motion exercises. The pain is much more bearable (no pain meds at all now for a couple of weeks), and I imagine we'll move to more strengthening exercises over the coming weeks...
Get thee to a PT!! It is well worth it on the road to recovery...