How to replace a text containing new lines using sed or any other method?

Hi,
i want to replace
"Hi How
are You when
did you go to
delhi"

to
"Hi How
are you when
did you come from
delhi"

in a file.

Any idea how to do it?

Is this a work related question, smells like home work to me...

Obviously its work related question.
I just simplified it so that it'll be easy to understand and try i take the clue and apply it.