Maria, it isn't as bad as you think it will be! All parents are v anxious beforehand, but usually children sail through.
We make sure we don't eat or drink in front of DS before operations, and change the morning routine to 'leapfrog' breakfast. Lots of distraction.
The anaesthtist wil come and talk to you on the ward - they might put a canula (thin plastic tube) in her hand, or they might make her unconscious with gas. If they use a canula, they will put anaesthetic cream on her hand 30 mins before inserting it. Distract!
You will be allowed into the anaesthetic room with her, you can take favourite toys etc, and will hold her on your lap while the anaesthetist puts anaesthetic into the canula. They fall asleep remarkably quickly. With gas they can struggle but the more they struggle the faster they go under as struggling increases their breathing rate. Or they may show her the screen and tell her the harder she can breathe in the more like;y she is to make it reach 10...can she do it....
It is hard seeing them unconscious. Most parents become tearful at that point.
They will come and get you once she is in recovery. Tell her straight away that the operation is over - DS sometimes comes round thinking they are still trying to anaesthetise him! Just be quiet and calm and soothing and let her gather herself. Have easy to eat and digest snacks available.
We have always just been very matter of fact about what is being done - just tell her the doctor needs to do whatever and that they will make her go to sleep while they do it so that she can't feel it. I have never said lost of 're-assurng' things because IME if you overdo re-assuring children become worried that there is something very bad over which re-assurnace is needed. WE have always just answered DS's questions fairly factually, and not made a big deal of it.
DS has had 9 GAs between the ages of 11m and 8.
I hope all goes well.