You do not note what type of spondylolisthesis you have (isthmic vs. degenerative-see website) and normally the L5-S1 level is an isthmic slip. However, ganglion cysts are associated with a degenerative slip so I will assume this is a degenerative spondylolisthesis.
If you have leg pain and lower back pain along with losing “30% of the feeling in my legs”, I would assume you would be a good surgical candidate. See the section “when to have lower back surgery” to understand this concept.
“Minimally invasive” spine surgery is a misnomer and a marketing ploy. 50% of the spine surgeries I do are revision surgeries (surgery to repair a pervious failed spine surgery) and most of these are repair of “minimally invasive” surgeries.
Find a well experienced spine surgeon who is meticulous and you should be happy. You can read the section “Questions to ask your spine surgeon”.
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.