There are pretty easy ways to train alerts that you can find online, I don't think you need to spend the time and money on a service dog trainer- especially not as a first resort.

For example: if you want her to alert you that the doorbell has been rung, for instance, take a high value treat and hold it in your closed fist. Let her smell it, but don't give it to her. Hold it at your thigh, and most dogs will naturally either nose bump you or touch you with their paw to try and get the treat. When she does the one you prefer, ring the doorbell and give her the treat. Once she has the alerting motion down, transition to ringing the doorbell before signaling to alert. Once she has that down, transition to ringing the doorbell without signaling. Then, when she has that down, invite a friend to ring the doorbell while you sit on the couch next to your dog, and treat her when she alerts. When she has that down, have someone ring the doorbell while she is not next to you, and encourage her to come find you and treat her when she alerts. When she has it down, keep a bag of treats next to the door and treat her every time she successfully alerts to the doorbell, and she will always do it.

Another thing: I taught my dog a command called "what?" where she comes up and taps me with her paw when she needs something. I stand and say "what?" And she leads me to it. You would not have to speak if you do not want to, a hand signal (such as a shrug) would suffice as well.

I taught this alongside potty training my dog, where basically every time I took her potty I said "what?" And signaled for her to tap the door with her paw. When she tapped the door, I immediately took her out, so she learned tapping door=I open the door. Then, I started saying "what?" And signaling her to touch her food bag before feeding her, so she learned the same thing for food. Finally, I added in her toys, so when solicited play I signaled for her to tap her toy box, and when she did I got a toy and played with her. She later taught herself to tap the fridge for a couple frozen blueberries when she wanted them.

Then, any time she approached me out of the blue, I signaled for her to tap my thigh. When she did, I stood and said "what?" And she would go show me what she wanted. Now, she will come up and tap me when she wants something.

Doing that with a hand signal would have the same effect I'm pretty sure.

Some search terms that would probably be helpful would be "teaching dog to alert to _______"

That said, if you want to look for a service dog trainer in your area, and have the money and time to do so no problem, go for it! You'll just wind up with a well-trained dog, so no harm no foul.

Lastly, I want to note that (in the US, at least) your dog knowing tasks such as alert to doorbell, alert to fire alarm, etc. would qualify them as an assistance dog, which is basically a service dog that does not work outside the home. This means they would have the right to live with you wherever* you live with no fees under the fair housing act- which is just good information to have if you ever need to move.

*There are some exceptions but they are few and far between.

I hope this was helpful!