I used to work with a guy who did this and he used to say repeatedly, "Flying the aircraft, no matter what aircraft, is the easiest bit by far." The real challenge is to learn to know what administrative, diplomatic, consular and other steps were needed for the specific countries you were in or flew over. But times change and there are now agents in place to assist in these procedures, I believe.
Having said that, on one occasion the guy above ferried a single seater from the US and was away a little longer than expected; when he returned I soon found out why. After shutdown there was smoke literally pouring out of the exhaust and inside the cabin on the floor were two OTHER turbochargers which had failed during the crossing. If I remember correctly, the second one failed over the Bismarck Sea and he had an interesting time on the shores of PNG. This fellow was very experienced and from what I understand had to use all his skills at that time to save his bacon. It's during these times that new aircraft owners appreciate an experieced pilot.