They will not be erased. You will be able to access your music files and previous settings once rekordbox is reinstalled (mp3 file import unnecessary).
Yes, rekordbox can only be installed after logging on as an administrator.
For a Macintosh computer:
Move the rekordbox program installed in the applications folder to the trash bin.
For a Windows computer:
From the [Start] menu, select [All Programs] – [Pioneer] – [rekordbox 2.x.x], then select [Uninstall rekordbox].
“2.x.x” indicates the rekordbox version.
The entire database can be deleted by deleting the rekordbox folder from the location below after uninstalling rekordbox.
C:\Documents and Settings\yourusername\Application Data\Pioneer\rekordbox
Mac OS X:
The Windows AppData and Mac OS X Library folders may be set as hidden. For instructions on displaying them, contact the respective operating system’s manufacturer.