change over vs revamp

change over

verb
  • to convert to, to make a transition from one system to another 

revamp

verb
  • To improve, renew, renovate, or revise (something). 

noun
  • An act of improving, renewing, renovating, or revising something; an improvement, renovation, revamping, or revision. 

How often have the words change over and revamp occurred in a corpus of books? (source: Google Ngram Viewer )