MB doesn't use hash values.
Any changes to a file, such as copying a file with the same file name, done from outside MB, such as dragging or copying from Explorer or changing tags, will require you the do a file rescan from within MB. Otherwise MB won't know that anything has changed. If the tags in the 'new' file are not the same as the tags on the 'replaced' file, it will be treated as a new file unless the old file was overwritten. You may see an exclamation point (!) next to a track. Hover over the ! and it will say something like "this file is not in its expected location."
Experiment. Make a copy of the file that is to be replaced and place it somewhere outside of MB's view. Replace the file with the new file and see what happens. You're not going to break anything as long as you only change a file or two. Once you see how it's being handled, and you're satisfied with the results, then you can copy over the rest of the files.