Prognosis of L5-S1 Grade II anterior spondylolisthesis and severe foraminal stenosis?

If there are any professionals out there...what's my long term prognosis at age 61 for longstanding L5-S1 Grade II anterior spondylolisthesis and severe right side foraminal stenosis; left side moderate to severe? At 40-radiculopathy symptoms began. At 48 could stand up for about 10 mins. By mid 50s I was Grade I spondy...could only stand or walk for about 10 mins without sitting down. (pain is reduced as soon as I sit). Since then, gotten R/L side epidural series every 12-18 months for foraminal stenosis related pain control, but still need NSAIDS frequently. P-Therapy did not help. By 59, a surgeon said I would need surgery from the front & back!! Had MRI 5/25/11..now grade II. Also had polio at age 4 (all 3 virus types) effected mainly left leg, right shoulder/diaphragm. Also have Peripheral polyneuropathy in both feet legs (worst on right side) from near fatal attack of severe acute pancreatitis with ARDS (11 days unconscious on life support).. Thanks!!!