EDIT: Total rewrite of question for clarity.I have a directory tree (new) with a bunch of files of with an extension of  .new. I have an identical tree (old) where many of the files have names identical to those in the new tree except that the extension is .old. I would like to copy all of the .new files from the new directory tree into the old directory tree which contains the .old files. As a file with a .new extension is written into the old directory tree, I would like to delete any file with the same name but a .old extension.So, if in the new directory tree, there is a file named new/foo/bar/file.new, it will be copied to the old directory tree as old/foo/bar/file.new and then the file old/foo/bar/file.old will be deleted if it exits.EDIT #1This answer was hashed out below (using the old question that had extraneous background information that was confusing). See the actual solution that I worked out below as one of the answers.
Need to copy files to existing directory and remove files already there with the same name but different extension
command line;scripting;find;file copy
This was the final answer that got hashed out in the comments for terdons answer.cd newfor i in */*/*.new; do cp $i path/to/old/${i} && rm path/to/old/${i//new/old}; done