As long as you COPY the CONTENTS of a known good library and TOTALLY replace the contents of the existing library, you are good.
Your OTHER settings (and plugins) are in your old (hidden)
C:\Users\<username>\AppData\Roaming\calibre
Replace that and you are almost good to go (if your OLD library was on a different path, calibre will not find it.Just right-click the Library icon:create-switch: USE EXISTING: <path to where you put the Library>