Surgery for the cervical spine generally will not increase range of motion. The exception is with pain generation associated with movement. Surgery that relieves pain will increase motion.
The sound of gravel in your neck is from wear of the facet surfaces. This sound by itself is not dangerous and is nothing to work about. However, it can be associated with pain if the joint surfaces are severely worn down and there is bone-on-bone contact.
Headaches can be related to worn facets at C2-3 and C3-4 (rarely at O-C1 or C1-2). Facet blocks (see website) will help to diagnose this disorder.
Donald Corenman, MD, DC is a highly-regarded spine surgeon, considered an expert in the area of neck and back pain. Trained as both a Medical Doctor and Doctor of Chiropractic, Dr. Corenman earned academic appointments as Clinical Assistant Professor and Assistant Professor of Orthopaedic Surgery at the University of Colorado Health Sciences Center, and his research on spine surgery and rehabilitation has resulted in the publication of multiple peer-reviewed articles and two books.