Jul 10, 2014 - 1:39 PM
In general the buses do require seat reservations, and the trains do not. You can best check the timetable for the details of the connection at your date and time. There are buses to either Domodossola or Brig, where you indeed will need to switch to a train. If a connection suggested by the timetable is marked with an 'R', you do need reservations.
Purchase options for the Swiss Half Fare Card are listed here. The 50% discounted tickets can be purchased through sbb.ch or locally at the station. It does not matter if you purchase the card first, tickets later, or vice versa. You just need to have both of them when you board the train.