Hi there,
its not recommended if you have a site that has a lot of content and customizations but it is possible.
The main thing is to do the switch on a backup or staging copy of your site.
When you import a new site it will a) add demo content b) swaps fonts and colors c) replace logos, menus, widgets, copyright d) add more Additional CSS if applicable.
Aside from correcting the changes those bring you would also need to review any customizations you have made previously.
And finally, the Dispatch site is due an update, it still relies on WP Show Posts plugin, which isn’t a block based plugin, its all shortcodes.
You may want to consider one of the other news style sites such as Newsroom and Info.
With those sites, you may just want to install one on a dev server and you could copy and paste the blocks you wanted to another site…