VRA Core plug-in installation

I'm trying to develop an omeka site and am a novice to coding...I'm currently trying to install the VRA Code plug-in (from Ethan at the Scholar's Lab). I unzipped the plugin and put the folder into my plugins folder, but when I went to the settings page in admin, it says:

The VraCoreElementSet-0.9 plugin cannot be loaded for the following reasons:

The plugin.php file is missing.

However, there is a plugin.php file nested further down in the plugin folder, so I removed the entire "VRACoreElementSet-0.9" and put back its contents, which is only a folder called "VraCoreElementSet" (inside of which there is the plugin.php file) ...unfortunately, now after I click the install button I get an error message saying:

The following error occurred while installing the VraCoreElementSet plugin: Name: Name of element set must be unique.

If anyone has any idea why this plug-in won't install, I'd really appreciate the help. Thanks so much!

Do you already have a VRA Core element set in your system?

You can check on the Element Sets tab of the Site Settings panel.

Hi John,
I'm not entirely sure- after I posted I noticed that the VRA Core was working despite the error messages I had posted about...I assumed it was magic, but perhaps the VRA Core was already loaded with the omeka installation. Unfortunately I have run into an additional problem; I try to type a name into the "agent" field, but always get an error message.

Agent: The "Agent" field has at least one invalid value!

However, when I type a number into the field, it works perfectly...do you have any idea why this could be? Thanks so much!!

I'm just starting to try out this plugin, and I'm running into similar problems. When I enter my first agent, and I put a name in the name field and enter birth and death dates, I get these errors: "Agent name is required," "'1820' does not fit the date format," and "'1901' does not fit the date format." I've tried formatting the dates numerous ways, with no luck. If I enter a number for the agent name, as ALD mentioned, that works. Then I can edit it and change it to a text name. Any idea what's going on here, and how we can fix it?

Thank you!