If you find that you have to do the same Find and Replace operation frequently, it seems like there should be a way to save it in Word don’t you think? I mean think of folks who work in document processing – how many times do you think they use Find and Replace for double spaces between sentences, or hard spaces, etc.
Unfortunately, I have to tell you that there is no built in method that I know of to save these Find and Replace operations.
It seems to me that the easiest method to do this in Word would be recording a macro that performs your Find and Replace operation. You can then run your Find and Replace with the ease any time you like on any document you like. I would suggest assigning a shortcut key to your macro or even assigning it to your QAT (Quick Access Toolbar).
There are third party add-ins out there if you do not want to use a macro. They may even enhance how you use Find and Replace. One I have found is MegaReplacer from Editorium. You can find it here.