Without being able to examine you or review your studies, it is impossible for me to determine wether surgery is right for you. Typically surgery is reserved for disease which can not be treated by medical treatment. Therefore, if you have failed physical therapy and medication is not helping then surgery may be the best option. I would recommend seeing a neurologist prior to surgery to ensure that your symptoms are related to your spine disease. Also if have not had an EMG, it may help to define the extent and degree of injury to your nerves.
Regarding the timing of a second surgery you should discuss this with your surgeon. If your symptoms acutely decompensate, surgery may be completed sooner rather then later. Please remember though that performing surgery does not guarentee that the pain symptoms will resolve.