How effective is DBS and at what stage of PD should it be performed?

My name is Dim from Bulgaria and I was diagnosed with Parkinson's disease 15 months ago, but I had the first symptoms more than 4 years before the diagnosis. I'm on medication like Mirapexine, Sinepar, Segalia and some others. The dose of these medications have been increased several times. The side effects of the medication are awful and they are getting stronger with the increased dose of the medications. And I have the most of them. I’m 52 and still actively working in the Armed Forces of my country Bulgaria.
Recently I find out about Deep Brain Stimulation as a method of treatment for the patients with Parkinson's disease. The closest facility where the procedure is being offered in is a hospital in Istanbul, Turkey by dr. Ali Zirh, who had performed approximately 1300 successful DBS surgeries.
Last week I visited the hospital in Istanbul and was consulted by dr. Zirh. According his prognosis, my condition will rapidly deteriorate in the next 2 years. His opinion was that I'm a suitable candidate for DBS procedure and I should be operated within a year time. I was provided with huge amount of information regarding the procedure and I feel lost.
After research hundreds of pages, I'm still not fully convinced with this DBS procedure. And I have doubts when, in which stage of the disease it should be performed.

Sorry for my English. It is not my first language, but I hope you were able to understand my questions.