ding dong, it's really gone!

My door bell does not work.

     The mailman came to the door yesterday and knocked because he rang the bell and .....pfft, nothing.
     How does a doorbell go bad?
     The front and back door are dead.  I thought maybe it was the button part, but it is strange both buttons would fail at the same time.
     So how does one go about fixing a doorbell?
     My first impulse is to buy a new one...but then it has to be mounted.
     You may remember:  I am a klutz!  I am not gifted at home repair.  Anything I touch turns to rubble, like a King Midas in reverse.
     I could call someone, but that can be expensive and it usually turns out I could have done it if I really tried.
     I don't think I have ever replaced a doorbell.
     This one had one chime for the back door and two chimes for the front door.  Or vice versa.  I could never remember.  I always went to the front door,and when no one was there, I would go the back door.  By then the people had gone around to the front door and were ringing the bell again.  It was like who is on first, only in real life.  With doorbells.
     I have to put it on my list of things to do when I am done playing solitaire and checking Facebook.
     I have several tasks on there already.
     I will give myself a window of between May 13 and Aug. 5.
     I will call myself first to verify a time.
     Notice I am using customer service tricks from companies that provide cable service or other types of service in the home.
     In the meantime, if you stop by, knock loudly.
    And if you hear loud music, just come on in, following the words of that old rock and roll spiritual:  "If the house is a rockin', don't bother knockin' just come on in."