I am running into the same issues. I have an existing site and wanted to switch to a GP theme. I was thinking that by importing a site theme (Newsroom), I would get the exact same layout and structure. Unfortunately, it’s not the case. Honestly, if installing a GP Site on a clean install of WordPress is the only way, this is quite disappointing. I am not a techie guy either, so I am in for some long hours of work here.