You can create a new site and leave the existing one in tact. Unfortunately there is no way to save the content from one site to another if you're changing templates so you'll need to build the new site.
To create a new site, click Websites Manager > +Add New Site
You can change which site your domain name points to by going to your domains page and clicking the change site association link.
I hope this helps info helps, let me know if you have any other questions.