Yes 2) works, but you don't want to be reimporting files that are already in your perfectly good Library. You could actually lose some information if settings aren't right. Re-importing is almost never the right idea.
Do 1), either by;
a) If you have copied everything from the original drive to the new drive, pulled the old drive out of the PC and put the new drive in its place, just make sure Windows gives the same drive letter to the new drive as the old drive had. The library will work without change. Make sure MC is shut down while you do this.
Google changing drive letters in Windows.
b) Similar thing if these are USB drives. Copy from Old to New, remove Old, change the drive letter of the new USB drive to what the old USB drive was. The library will work without change.
c) If you are adding a drive, let's say the old drive was D: and the new is F:, use the "Find & Replace" function of the
Rename, Move, and Copy Files function to simply replace all instances of D: in the Library with F:. Read the Wiki article carefully.