Surgery is a very scary prospect. I had to have my wisdom teeth out a few years ago (age 27) and was TERRIFIED over such a simple "surgery". When I got there, I was given something to relax me which was typical before the procedure and it REALLY helped. I wish I had something in the days BEFORE the surgery as that would have helped me out too.
In your case, I would definitely ask your surgeon if you can be prescribed something before the surgery. It is also important that you tell the surgeon that you are prone to panic attacks so they can treat you appropriately before the surgery - they may also give you something to calm you down as the surgery gets near.
It never hurts to ask about getting something to help you relax for the surgery. You may find, that on the day you are calm and do not require anything but it is reassuring to know you have the option of taking something if need be.
I can understand how you feel, I get nervous as well. Do ask for medication there is no harm in trying. I wanted medication before an angiography, I was terrified! They wouldnt give me any but this was only because it was brain related and they needed me to be alert - I had to be awake. They might give you some before any other surgery. My experience of anesthetic has always been good I would rather be unconscious! You will be in good hands so try not to worry!