You are right that the stations are spaced out differently on the dial. A digital tuner will miss some stations entirely, tune some in just fine and a few will be there, but not tuned in correctly.
Europe has had digital broadcasts for several years. I understand it is slightly different than HD radio which is coming to the US. He may want to switch head units when he gets here to take advantage of the digital broadcasts.
Regarding the navigation discs, GPS is the same format around the World, so there should be no issue. He should make sure he gets the latest updates on his navigation discs. Especially in the eastern part of Europe there are major changes occurring regarding highway construction, city renovations and even national borders. My system is only a year old and already I need to get an upgrade, because of these issues. Poland is currently constructing their highway network, similar to how we did in the 60s and 70s. Travel currently is by two-lane roads (think Rt 66), with only short sections of "interstate highways" completed.