It has always been my understanding that the only changes that you need to do are:
- install the SSL cert on your web server.
- configure your webserver to use ssl.
- (optional) force http to https at the server level
- change your Admin panel -> Settings -> System -> Helpdesk URL to have a https:// prefix
If you need an Apache .htaccess you could do it something like this (note: this is not tested!):
RewriteEngine On
RewriteCond %{HTTPS} !=on
HTTPSRewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^ https://www.domain.com%{REQUEST_URI}