An update on my setup. I used the Surface with Maps Pro and downloaded files of US and Canada, a GlobalSat antenna for 34 days, 9220 miles without any significant issues. Google Maps files that I converted to KML worked fine, as well as GPX files from the trip coordinator.
The only problem was that I occasionally had to restart because the GPS cursor wasn't aligned with the displayed map.
The big screen was awesome for both navigator and driver.
We went through the Canadian Rockies, Cascades, and multiple US areas without any data connection.
When in data I had the option of running my phone hotspot and use Google Maps for directions, but Maps Pro worked just as well.