S.W.
My daughter (now 10) had numerous ENT procedures the first at 9 months. Her adenoids were removed around the age of 4. We have always dealt with new issues through education. There are a lot of "I'm going to the Hospital" type books available (I specifically recall one called "goodbye tonsils" when she later had her tonsils removed) These books help explain what will happen and what she can expect. If she's not been exposed at all to the hospital setting, I think it would be worth your while to visit the surgical unit before. Children's and BTNRH will allow this and you can show her the mask they will place on her face, etc. They always gave my daughter a liquid "relaxer" prior to taking her back to surgery or putting in any lines, etc.; she was typically asleep prior to even leaving the room. Both area children's hospitals are well equipped with toys and do an excellent job of catering to children. Jammies have cartoon characters, nurses explain what is happening to the child, etc.
We also always took a special wrapped surprise that she could open after surgery (a new Barbie or something she really wanted). After surgery at home, we made "sno cones" using crushed ice. I found the flavored syrup at Target and this was soothing and different for her.
My daughter always came through like a trooper and I am convinced it was much more difficult on us, the parents, than the child! Above all, be brave for her and look upon it as an adventure. If I can be of further help, please feel free to contact me. I am confident all will go well = good luck!