What can we expect when moving an automated implantable cardioverter-defibrillator from the abdomen?

A fellow caregiver asked...

My husband has hypertrophic cardiomyopathy and has had a defibrillator for more than 20 years. He goes into the hospital this week for yet another replacement. This time though they are going to remove the device from his abdomen and implant near his clavicle. They plan to leave the old leads in since they've been there so long. I wish this procedure it easier but scares me to death ever time. Any words of advise for this upcoming procedure.