Maybe start with working out why you fear the operation in the first place/asking questions where that'll help reduce your fear? I think some fear of surgery is rational (my own personal fears are of waking up in the middle of the operation, of dying during it due to complications with the anasethetic and of waking up and not being able to open my eyes 'cos they're covered in tape) because there are some risks involved in it. Doctors ought to be very used to talking to people about their fears of surgery and may be able to provide reassurance on some bits and pieces.