Hang in there. It's not that bad. I had amniocentesis with difficult child 3 and I was very apprehensive but it was OK. I was a bit shaky afterwards, but I think that was the aftermath of being so nervous. It was interesting watching my baby on the screen, dashing here, there and everywhere. He was moving so fast...
The other thing they will probably order is an anomaly scan. It's a very detailed ultrasound. I had it done at about 26 weeks. It was fascinating to see my baby's facial features. But we also were able to check out his kidneys (there is a congenital problem in the family) and follow the ureter from the kidney down to the bladder to make sure it was not malformed or duplicated. And that ureter would have been thinner than a cotton thread! They checked the chambers of his heart, made sure it was working properly and the valves were all doing what they should... the detail was impressive. And of course, we could see for certain that he was a boy. I had mother in law with me so she could see it all, too. I remember when the scan was being done, the sonographer was talking to me about the various things you would expect to see in Downs.
Don't let it freak you out too much. Even if the tests are positive for Downs, you don't know how affected the child is, until she's born. There are degrees of Downs and some live normal lives.
A lot of the tests err on the false positive side rather than false negative. Also, friends of ours from church had problems like this with their daughter's baby. The baby girl was diagnosed, in utero, with some sort of trisomy problem (not Downs but something else) plus she had all her intestines and liver growing outside her body. There were also bands of tissue around her wrists which were threatening to cut off the blood supply. Left unchecked, she would have died within hours of birth and would also have been born with hands gangrenous. But with the trisomy, they felt that she wouldn't have quality of life anyway and were going to let the baby die. Then they discovered she didn't have the trisomy after all. So they operated on her, in utero. The bands of tissue were released, the intestines were put back inside (not easy - there wasn't enough room for them because her body hadn't been growing properly).
When the baby was born, she was perfect. Except for a trace of problem with one wrist. She's grown up well, still favours one hand but only slightly. Otherwise - a blonde-haired moppet, a bright spark.
That case featured on an Aussie hospital show, a reality TV that was showing success stories. Then later on we met the family and could see the great result for ourselves.
So you never know!
Marg