S. Korea's $2 billion welcome mat for '88 Olympics

Since Seoul was chosen to play host to the 1988 Olympiad and the 1986 Asian Games, South Korea's national image has been energetically under reconstruction.

The government is determined that the 4.5 million visitors expected to attend the two events will be impressed - not only by Seoul's splendid sports facilities but also by the modern charms of the capital city and its inhabitants.

The Olympic Games are expected to cost the nation more than $2 billion - or, as one estimate put it, about $60 per person. But fears of possible financial problems are dismissed by Seoul's Olympic Organizing Committee, which says that revenues from the games will largely offset the costs.

Anyway, it is implied, Korea is willing to pay for the international prestige of being the first developing country and second Asian country, after Japan, to play host to the games.

Most Koreans seem to agree with the committee's view. ''Foreigners only know us through the Korean war; this will give us a chance to show Korea to the world ,'' a Korean housewife said.

Sports facilities for the games are well in progress. At the Jamsil Olympic complex, a 25-minute drive from the city center, a gymnasium and swimming pool are already in use. The main stadium, which will hold 100,000 spectators, is expected to be completed early next year.

An equestrian park, velodrome, rowing and yachting basins, and another gymnasium are also planned, along with apartments for 13,000 athletes and officials and a press village for up to 8,000 foreign newsmen.

But preparations are by no means restricted to sports facilities. Work recently began on the polluted Han River, which runs near the Olympic site and through the southern part of Seoul. A $464 million transformation is planned for an unappealing 22-mile stretch of river where murky waters now slip past refuse-strewn mudbanks.

A 180-mile pipeline will divert the millions of tons of untreated sewage, now being dumped into the Han, for proper treatment. Riverside parks, recreational facilities, jogging and regatta courses are also planned.

Limitations on building heights have recently been relaxed, and throughout central Seoul squat, ugly buildings - thrown up in haste after the Korean war had razed the town to the ground - are being torn down and replaced by tall, shining, concrete and mirror-faced tower blocks.

Much of Seoul's dense traffic is temporarily supported by metal plates instead of roads as new subway lines are hewn out beneath the town. A plan to plant millions of trees aims to convert this noisy, crowded, concrete capital - the fourth most populous in the world - into a garden city for its nearly 9 million inhabitants.

With all this, the government has not forgotten that ''manners make the man'' and that men and women make a city. Certain Korean customs, deemed likely to offend visitors, are being revised. Snake and dog restaurants have been ordered to move to the less visible back alleys. So-called ''decadent entertainment places'' have recently been subjected to police raids and closure.

The government has published a 178-page ''guide to basic behavior'' to help Koreans, comparatively few of whom have traveled abroad or had much contact with foreigners, to make a good impression and cope with the strange habits of foreign visitors.

The handbook gives guidance for various situations; on the street, Koreans are told not to blow their noses, smoke, drop litter, or wear pajamas, for example. In a foreigner's house, not to open an umbrella, go to the toilet too often, or pick up the crockery to see where it was made. At sports matches they are told to applaud foreigners as well as Koreans. They are warned not to ask a foreign woman how old she is or how much she weighs.

Most foreigners find Koreans naturally courteous and helpful, and their customs interesting, often charming. But just in case visitors are not sufficiently impressed with the signs of material progress, the handbook urges Koreans not to feel inferior and suggests, ''tell your foreign friends that our spiritual civilization is a step ahead of theirs.''