How complicated is the setup for the Internet?
It is pretty straight forward. You need a mobile device (Android or iOS) temporary just for initial connection setup. You use Ambients awnet app to set it up.
Do I need to configure/open ports on his firewall for this to work?
No
Would it be better to configure it in my home and get it working and then move it to his network?
No. Unless you go through the trouble of configuring your home WiFi to be exactly his wireless SSID name and password Key. I mean exactly! Case sensitive and spaces and all. Then you can power down and move the console and just plug it in at his place and it should see the same SSID network and with the same wireless password key and just connect to the Internet. But there is more to the configuration than just Internet. You'll likely want to also configure Weather Underground, Ambientweather.net and maybe even WeatherCloud as a backup so that it sends data to all of them. Remember that every few months you may want to do a firmware update, so you'll need your mobile device to be there at the home location to update it. Remember to do physical maintenance of the station especially the rain gauge cleaning...etc.
Is this entirely independent of needing a PC or mobile device once it's working (the owner of the home uses a flip phone!).
Nope doesn't need anything running at the location but for the WiFi router to be running and have service. And the console needs AC power (batteries only backup data and are not used to run WiFi connection). If brownouts or power outages are a concern then consider a battery backup (UPS) for the console and router.
Our primary interest is wind speed/direction and outdoor temperature.
Then make sure you get a good siting.
Good guide to follow even if you don't plan on uploading to CWOP:
https://www.weather.gov/media/epz/mesonet/CWOP-Siting.pdf
