You will need to file a deletion request through the site first, then I (or another agent) will be able to remove the local for you to replace.
You can use the Delete Video
page, available on the site under Editors > Edit Video Info > Request Deletion of Bad Video Entry (the last link is at the bottom of the page). There you'll be able to specify video ID and reason for the request. Just state that you have a higher quality copy and thus want to replace the local and it's fine.