How dangerous is a spinal Fusion ?

I don’t have idiopathic scoliosis , mine has a specific reason due to muscular imbalance after a neck surgery which damaged a nerve in my neck but my spine is slowly getting worse and shifting as years go by.

I want to know how dangerous and difficult is a spinal fusion if my spine doctor ever recommends it ?
I am also 36 right now. So surgeries might be harder as I get older.