Is Geoserver's "styler" plugin dead?

The OpenGeo Suite's GeoExplorer now has the styling capability that Styler used to have. That must be why they shelved it.

You can get the code and installation instructions at Github.

The REST plugin no longer exists for GeoServer as it has been incorporated into the core. You should not have to install anything, the REST API should work out of the box. You can test by using the URL:

http://localhost:8080/geoserver/rest

The GeoServer documentation provides some good information about the REST API.