Here is what you can do.Just try to update your site to redis using update command.If that gives an error saying not possible....you can create a dummy site with needed options and rename the site specific conf file in etc/nginx/sites-enabled with that of your domain name change paths accordingly.Also disable w3tc plugin beforehand and download redis object plugin dont enable it just yet.Do it only when you determine the site runs without a glitch.If run into boo boos you can revert back by using your original backup conf file.
Once again kudos to ee and bow to the mighty Nginx.