I'm not sure how old your baby is, but my sister adopted a toddler from China with a very very severe cleft palate. His teeth had already come in, and were sticking straight through the front of his lip under his nose! After she brought him back to the states - he has had several surgeries in the last two years. After the first - he had some minor complications with seizures from the pain meds - but they just keep him a little longer in the hospital now and really watch him closely - no more problems. He has a slight speech impediment - but I think that it has more to do with having to learn a second language so different from his own at the age that he would have started talking and having all those surgeries in his mouth. He seems to hear just fine - and responds to speech when up close and when he is across the room or pool or wherever! The only thing that my sister is extremely cautious about with him at this time (I mean in regards to the cleft, and surgeries -still concerned about all the normal stuff) is one time when we were together because she was visiting FL - I saw him standing with someone else and he had a straw in his mouth. She couldn't get it away from him fast enough because if he stumbled or pushed it in the wrong way he could have really caused alot of damage.
On another note, my niece had a baby 2 years ago, and while still in the hospital they tested her hearing and she failed. Follow up testing revealed that she was born with severe hearing loss - I don't remember exactly - but something like 40% in one ear and 80% in the other. She has custom made hearing aids fitted a couple of times a year, and has a speech therapist. She already is able to follow directions, respond when spoken to &is learning to talk. It hasn't affected her in any other way - she is happy, well adjusted and seems to be getting along just fine!
I guess I don't really have any advice, just words of encouragement. Keep your chin up, I'm sure she will be fine. Kids are very resiliant, and he may just be telling you "worst case scenario" stuff just in case. I'm sure she will be fine, and if she has some hearing loss, she too will adjust. I don't want to sound crass or mean - like I'm dismissing it or anything, but goodness, there are are alot worse things that could happen!
& PS: my nephew that has had the surgery - by the 6th month after surgery - you could barely detect a scar, and now........not at all! (he's 4 now) Good luck, and God Bless!