Haha I didn't find it hard. Worst case you can do corrections. Say you buy a ticket and actually needed to go further, you can pay the difference at the end. Or get a rail pass and go on a journey somewhere before it expires
You can't activate the rail pass at the airport. So you need to pay from airport to tokyo. Ticket from Tokyo to hakuba return is only half the cost of the rail pass so you don't really need it