Cori,
There are several types of neck dissections. There is the radical which removes the SCM muscle, the jagular vein, the spinal accessories nerve and lymph nodes. Then there is the Modified radical which preserves the nerve and there are others where only the lymph nodes are removed.
What affects the movement of the shoulder or arm on the side of the dissection is weather the spinal accessory nerve is preserved, removed or damaged during the surgery.
My family member had a modified radical neck dissection where the nerve was saved. There is no damage or loss of movement to arm or shoulder on the side of the dissection. The hospital stay was two days and recovery time from the surgery was about 6 weeks.
Radiation and chemo however were done following the surgery.
Best wishes to you and your brother.