A country changing direction of driving (from right to left)

For people in the United States, Europe, and many other countries, drivers drive on the right side of the road, and are totally used to that way of driving. When they arrive in countries that were earlier part of the British Empire such as India, Australia, New Zealand, and of course, Great Britain, they are not used to suddenly seeing vehicles driving on the wrong side of the road (in these countries, people drive on the left side of the road). It can be very unsettling, and for people moving from one type of country to another, it can be very difficult to drive on the road; it takes time to get used to the traffic coming from an unexpected side. So, what happens when a country (even if it is a small country) decides to move from one side to another, and that too, the reason being that importing cars are cheaper (link to article):

Samoa will switch its driving from the right side to the left side of the road on Monday in a move opponents have called ill-conceived and said will lead to dozens of wrecks and fatalities. Proponents tout the change, which no other country has attempted since the 1970s, as making economic sense.
The nation has declared Monday and Tuesday holidays for people to adjust to the change and banned alcohol sales for the next three days. Until now, most of the cars in the Pacific island nation have been imported from the United States, where drivers travel on the right side, and Samoa's neighbor, American Samoa. The change will allow the thousands of expatriate Samoans who live in their nation's biggest neighbors, New Zealand and Australia, to send used -- and therefore, cheaper -- cars to their families back home. In both those countries, drivers travel on the left side of the road.