First Appointment With Pcp For 3 Month Diet

I have my first appointment with my PCP for my 3 month medically supervised diet on Thursday August 9th. Do I make the appointment at his office with the nutritionist or does the surgeon help me with that? I don't have my first appointment with the surgeon until September 7th but the lady at the surgeon's office told me to start with the PCP before I see the surgeon. And what do I tell my PCP when I get there? He made my referral to the surgeon but I just want to do everything right to make the process easier with the insurance company (Cigna).