Not sure why you would need to edit any core files if you have properly enabled SSL AND created/installed your SSL Cert using Plesk/cPanel. The server should automatically redirect to the HTTPS:// domain.

It's also important to note that if you do successfully enable SSL for your website, you will need to reset your UNA license and create a new key/secret using the full https:// domain name or else you will not be able to connect to the market.