SUNDAY'S overwhelming vote for Ukrainian independence was the culmination of a nationalist movement that reshaped that republic's politics over the past few years.Genuine independence, however, remains more a goal than a reality - though it's a goal endorsed by almost 9 out of 10 Ukrainian citizens. Of first importance to the government of newly elected President Leonid Kravchuk, the Ukraine's economic house has to be torn down and rebuilt. The republic is an agricultural powerhouse, producing as much as 46 percent of total Soviet farm output in recent years. Most of this production comes from huge collectives. Breaking them up and giving private farming a start will be a slow, difficult process. The same holds for Ukraine's state-run heavy industry. Ungainly problems remain from the days of union. Soviet foreign debt has to be apportioned among the various republics. Ukrainian officials have said they're willing to pay their portion, a commitment that will be watched closely abroad. As the Ukrainians were voting Sunday, the Russian Republic assumed responsibility for the Soviet Union's payroll. Clearly, Boris Yeltsin - not Mikhail Gorbachev - will be the key figure both in divvying out leftover financial obligations and in forming any new compacts. The Ukraine recently signed Mr. Gorbachev's proposed 10-republic economic cooperation plan, but Mr. Kravchuk now wants no part of the plan. Still, Ukrainian leaders have little choice but to work closely with Yeltsin's government. The two republics are intertwined economically. Russia is the only market for Ukraine's agricultural products. Russia also supplies Ukraine with oil and raw materials for its industries. The euphoria of nationalism and independence will have to give way to practical considerations of keeping the Ukrainian economy alive. Political tensions could surface both within the Ukraine and with Russia. The republic has religous, ethnic, and cultural divides. While many of the Ukraine's large Russian minority voted for independence too, its rights will have to be carefully observed to avoid conflict with Russia. The Crimean region of southern Ukraine, heavily Russian in population, only became part of the republic in the 1950s under Khrushchev. It could become a point of contention between Moscow and Kiev. The reasonable path for the Ukraine's leadership is negotiation and cooperation with Russia and its other neighbors. Unbridled nationalist fervor, brewing over from Sunday's vote, could work against that.