Hi there,
we don’t recommend installing a Site from our library on a pre-built site.
Part of that process will import content and change some elements such as your menus and logos.
But it WILL NOT delete any of your existing content or change their permalinks/structure.
If you want to try to change to Dispatch, then i suggest you create a Staging site and then do the import, make any fixes to your site and then if you’re happy push the site to live.
Your Hosting provider should be able to help with Staging Site.