Can I edit an audio/mp3 file and do changes in the lyrics ??
For very simple editing, take a look at Audacity, however, to do what you want is very awkward - you will need to record the edited lyrics, then mix them together - Audacity allows you to do this, but it isn't the easiest thing in the world.
This will depend to some extent upon how the audio contained in the MP3 file was mixed. If:
then you'll have a reasonable chance of lowering the level of the vocals, relative to the rest of the audio, to the point where mixing in a new vocal recording will effectively mask them.
Here's some good advice for someone else who asked a similar question.