Hi there!
In addition to the grade, the decision of a surgery would depend on the type of spondylolisthesis and the associate symptoms. Initial conservative management (physical therapy/ anti-inflammatory measures/ pain management/ braces) may be tried before considering a surgery. Surgery is typically considered in severe cases or when there is compression of the surrounding structures. It would be best to discuss the management plan in detail with your treating orthopedician.
Hope this is helpful.
Take care!