The literature shows excellent results for lumbar spine fusion. 90%+ successful fusion rates are frequently reported in large randomized controlled trials and same with patient satisfaction. A three level fusion is more difficult than a one or two level but still shows decent success. The product and technique used will also play a role. My advice is to ask your surgeon for the name of the technique he would use and then Google it. Look for the studies and read the results. That will give you an idea of the typical success rates and patient satisfaction with that particular procedure.
Right on. smoking has been shown to have a negative impact on healing.
Really? I think either you might have misunderstood or your doctor is misinformed. I'm not even sure what documented by the mayo clinic means... that they published a study? This is easy to disprove, simply read through the studies online to see the average success rate for lumbar fusion in large patient population is much higher than this. Again a 3 level will have a lower success rate but recent literature should put it at around 70-80% successful fusion with low pain reported.