I have a SD that I got my second year of college (I’m in the last semester of my 4th year now) and it was honestly a mixed bag and a pretty complex experience.
I don’t think they would help at all when driving, but you could look into things like audio-tactile/visual conversion and siren detectors for that, if you haven’t already!
My SD can help quite a bit with sound detection and direction (along with some other tasks, she’s multipurpose), though, and she can make me feel more comfortable with being HOH both in public and when I’m alone.
I think the thing that a lot of people don’t necessarily know about being a handler is how hard it can be, and my first year with mine was really tough. Pre-trained dogs are extremely expensive (like up to $50,000) and there a very few training programs for hearing dogs. It’s also usually a several year waitlist for a trained dog, and you’d have to then travel to and stay at the training grounds for several weeks or even months sometimes to finish their training. Because of this, I think most people (including me) try to do a form of self training. This was what I found to be the most difficult thing, because it’s a lengthy process and really draining, especially for someone with any kind of disability already. You have to find a dog or puppy-raise first, then pay quite a bit for a trainer, and then just go through the training, which usually takes over a year at least to even get things like public access trained (aka the skills of heeling, sitting quietly, tucking under chairs, ignoring people and other dogs, staying, etc), then even more for specific tasks (like sound detection). I almost failed out of school while training my dog tbh lol.
Things got way better after that, though, and she does help me quite a bit now! She does still takes up a considerable amount of my energy through the school day, and don’t even get me started on having to deal with stuff like rude people, access problems, etc, but overall it can be really rewarding and worth it for some people.
I think for things like hearing loss, though, I’d honestly suggest just looking more into adaptive tech and maybe getting just an emotional support dog (an untrained dog that provides support for someone at home, which you can get into the dorms at colleges with a dr note.) An ESA may help you feel more at-ease when relaxing, since they can at least naturally do sound alerts by looking at the door when someone knocks and stuff like that.
Lmk if you want to talk more about service dogs or ESAs or anything, after i trained my own dog I became pretty passionate about helping other people in this area :)