Hi we recently went through a similar thing, I had my first baby in November and I also have a 10 year old Springer spaniel (aged 9 at the time) who really struggled at first with the crying and noises and also the fact he was not my main focus anymore. Although I must admit he was never aggressive but he is a boisterous and very busy dog, if you were sitting down or standing while holding her he would constantly try to jump and grab her and if she was in her cot he was up at the side of the cot constantly. It wasn't aggressive but he was trying to grab her almost as if she was a toy 😳
What fixed it was mainly extra obedience training, time and managing the situation. He is pretty obedient anyway but we had a dog trainer in to assess the situation as I felt out of my depth and struggling as well with feeling guilty about how my dog was feeling and trying to cope with becoming a mum!
We really worked on the leave it command, he is really good at this normally with food etc but the crying was really working him up and blowing his brain so everything he knew was going out the window. We practiced 'wait' and 'leave it' over and over until he would do it no matter what. We would also put the baby in her cot in the living room and get him to sit 6 feet away from the cot - reward when calm and gradually reduce the distance until he would sit right next to the cot without trying to jump up. The same with having someone holding her whether they were standing or sitting we repeated the same thing. He was on a lead for this as well so we had total control of him and if he did try to jump we could correct him without there being any risk to our baby.
As my baby suffered badly from colic she did cry a lot and i won't lie our dog was stressed out sometimes but we made sure that he was walked a lot and sometimes he stayed at my dads house to give him a break from it for a few hours.
I would also add we have stair gates everywhere and he was never allowed in the same room if she was on the floor etc. Now over the last couple of months I have relaxed this slightly but I rarely let him him still as he's a lump of a dog and i don't trust him not to step on her accidently.
He is completely unbothered by her now 6 months on. It did take I'd say about 3 - 6 weeks before he calmed completely though. It did take some work which is really hard with a newborn but it will all be worth it because my dog will now sit on the couch next to her while the baby plays with his fur. Unfortunately i don't have much advice for aggression as we didn't have that issue it was more him being out of control from excitement i believe or being stressed out from her crying but if you get a good dog trainer in I'm sure you'll be able to come to a solution.