If your doctor is a woman, you are guarenteed a built-in level of empathy which a male doctor cannot provide.
Be absolutely honest about how frightened you are, and ask if you can have a mild tranquilsier prescribed for the day to take the edge of your fear.
It will probably be a lot less traumatic than you fear, but you need to get over your anxiety in order to get these proceedures completed, so make a 'chat' appointment with your GP and tell her how you feel. i am sure she will have dealt with this issue many times before, and able to sympathise, and reassure you in advance.