Door bell wiring

Hi. I have a Milliken (may be mis-spelled) exterior door with two side light panels on both sides. I have purchased a Larson Storm Door for the front door. There is not enough depth between the two doors when measuring them - therefore I need to build the front door frame out. I need to know...

How can you tell if your door bell is done working? And if so are they hard to replace? I am a single woman?

I would like to know what the circuit of a door bell (front lighted button) no back door bell, how it is wired with four wires. Two solid blue and two blue/white. Four each on the transformer ane four on the bell transdusher. Two on the button, front door. How does this work?

I move to this House, and the door bell sound more like a alarm than a door bell( is extremely loud and irritating). The ringer brand is bticino (model 382321 made in Italy). I been looking to change this one to a more easy to listen chime or bell. But everything I found is an external bell box....

I'm replacing just the ringer part of the doorbell (the type of doorbell with a transformer). Should I shut off the electricity when doing this, or since they are low-voltage wires is it OK to install it with the electricity on? Or is this a stupid question ;) The way the electricians wired our...