Namibia: Realism Key for Economy. Guerrilla incursion increases doubts about SWAPO's political and economic savvy. SURVIVING WITHOUT SOUTH AFRICA

GORDON MERRINGTON remembers all too well what happened after the revolution in neighboring Zimbabwe. A North Korean political commissar was assigned to the office of Mr. Merrington, a housing specialist. His job: to monitor Merrington's telephone calls - even though he didn't speak a word of English.

``It was a total waste,'' recalls Merrington, who now lives in Namibia. ``It seems every time a liberation group takes over a nation, they feel obliged to remake the economy. I just wonder if we're going to have to reinvent the wheel here, too.''

His is a legitimate worry. For on April 1, this southern African territory started down the road to independence after almost 75 years of South African rule. That's when a plan took effect for a United Nations-supervised transition to elections in November.

But then hundreds of guerrillas from the South West Africa People's Organization (SWAPO) allegedly came charging over the border from Angola. At least 300 rebels and members of South African-backed security forces died in the clashes, which ended with a cease-fire arranged last Sunday. Under the plan, SWAPO fighters are supposed to gather at designated assembly points to be escorted back to Angola by the UN and confined to bases there.

Analysts reckon the incursion either was a terribly miscalculated attempt to set up bases here - thus violating the UN accord - or the work of a breakaway faction. (SWAPO claims its soldiers already were here and were fired on by security forces.) Either explanation raises questions about whether SWAPO, the group most likely to win an election, has the coherence and savvy to run the place - especially the economy.

For analysts warn that while SWAPO will inherit a workable economy, it will have to do some sophisticated and unrevolutionary things to keep it that way. As a start, it will have to tread lightly around South Africa, which controls vital transport routes. Last week's battles showed Pretoria's willingness to come down hard on those its deems threatening.

SWAPO also will have to take care not to scare off the country's whites, with their needed skills and capital. That means no radical tinkering with the economy. For the stakes, analysts say, could not be higher: a matter of making this place a Botswana - southern Africa's showpiece of economic stability - or a basket case.

``If the ruling party goes for an orthodox Marxist orientation, we'll go down the drain,'' says Fanuel Tjingaete, a University of Namibia economist. ``If it's realistic, we'll survive.''

Compared with the sorry state of many of its African neighbors, Namibia has a lot going for it: great mineral wealth; South African-built roads and rail lines; relatively few people to feed (about 1.5 million). The UN has trained 2,000 bureaucrats for the new nation at a SWAPO school in Zambia. And scores of Namibians received college educations on foreign scholarships - a far cry from the handful of university graduates nearby Mozambique boasted, for instance, when Portugal pulled out in 1975.

But what SWAPO inherits could stymie even the most experienced of governors. The economy grew an average of only 1 percent per annum from 1971-85, mainly due to drought and a drop in world prices for base metals and minerals - the country's big cash earners. This, while the population increased at about 3 percent annually. As a result, unemployment is running at around 30 percent; some economists say it could hit 50 percent by 1995.

Moreover, about 16 percent of the country's budget has come from direct South African subsidies - funds that will be cut come independence. In addition, economists say Namibia has run up a sizable debt, though no one's sure just how sizable since Pretoria doesn't publish those figures.

As Mr. Tjingaete sees it, ``We could be headed for trouble. Our economic base isn't expanding, but our socio-economic problems are.''

SWAPO shouldn't be tempted by what look like quick-fix solutions, says Merrington, who heads a firm that builds low-cost housing. Big-ticket development projects are first on his list of post-independence no-nos, because ``the UN right away will want to send in the clowns: consultants and experts who will descend upon us like hordes of flies.''

(Merrington says Zimbabwe's first $1 million of foreign debt was incurred in hosting a UN development conference to which an expert on harbors was sent from New York. Land-locked Zimbabwe doesn't have harbors.)

He also warns against doing ``the usual revolutionary thing'' of abolishing all vestiges of colonialism - such as changing the currency (in this case, the South African rand.) That, says Harold Pupkewitz, who owns a building supply firm, would be a disaster.

Mr. Pupkewitz says he currently can buy 1 million rands' (about $393,000) worth of goods just by sending an order to his South African suppliers. If the country changed currencies, he would have to purchase letters of credit. And that would tie up precious funds.

Getting cut off from the South African market would have other harmful effects, says Pupkewitz. For instance, almost all his materials come from Namibia's southern neighbor. A truckload of cement, he reckons, takes only two days to get to Windhoek. And while he can buy from South Africa in just about any quantity, tiles from East Germany, for example, have to be ordered in large shipments.

Just now, it's hard to pin down exactly what SWAPO'S economic policies would be were it to take over. In recent years, it has veered from pushing Marxist policies to those of a mixed economy. But with elections looming, SWAPO members are tight-lipped on specifics. But they do talk a lot about trying to keep whites from emigrating. (Some 25,000, or one-quarter of the white population, fled 10 years ago when independence seemed imminent.)

``We are appealing to our white brothers and sisters to come forward to build one nation,'' declares SWAPO Central Committee member Crispin Matongo. ``Whites must feel free, feel at home. Everything they have will remain theirs.''

That's little comfort to whites fed a steady diet of South African admonishments about Marxist SWAPO demons. Skepticism is especially high now, after the SWAPO incursion. On the face of it, most are taking a wait-and-see attitude. But one businessman says, ``It would be completely naive to think that everyone isn't creating a fall-back plan.''

``We're hoping the harsh realities of this place will have a sobering effect on SWAPO,'' he continues. ``We understand that it's a fragile economy. We hope they do, too.''