Unless you work really, really hard, getting a PhD in a period of two years is not as easy as you make it sound. Of the MD/PhD students at my school, I know of only one (or possibly two) who completed a PhD in two years between the second and third-years of medical school.
Typically a PhD candidate will take anywhere between three and six years to finish everything.
Being a DO going into surgery, where old biases exist at most programs, is sort of an uphill climb though not impossible. During my interviews I met only one DO resident at one university program in Philadelphia, PA. He did incredibly well on the USMLE (not just the COMLEX) Steps 1 and 2, had a few papers under his belt, but overall had nothing else academic going for him. He told me he had a great connection over at PCOM, where he attended school.
I think if you can emulate what this guy did, then you'll be a shoe-in at good surgical programs. Harvard's Mass General, the Brigham, or BI-Deaconess probably not, but a good program nonetheless.
But a PhD will help you if you have mediocre numbers at the time of application, and will even help you in a fellowship search later I believe.