I can just tell you that I had a lung infection before, during, and after my surgery, and coughed hard and constantly. My wrap held strong and I did fine. I would suspect that yawning is much easier on your healing wrap than the severe coughing I was doing, so I think you can relax.
Glad you've joined the forum! It sounds as if surgery was exactly what you needed. I can understand your hesitancy to get the Nissen. Like you, I held off far too long because of reading those scary posts. Shortly before my surgery I found this great forum, and the people here provided me with great information and support.
Since there was precious little positive and helpful information online, I've stuck around to help others the way I was helped. Hang in there, and good luck with that yawning! Just remember that healing from this surgery takes a full six months for most of the healing, and a year for the rest. It'll take patience, but if you can surrender to your recovery and go with the flow, you'll do just fine!
Nissen Fundoplication 2/09
"Whatever you fight, you strengthen, and what you resist, persists.”
“Worry pretends to be necessary but serves no useful purpose”
“Accept - then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.”