THE events in Moscow last week demonstrated dramatically the momentum of reform today in previously authoritarian societies.They were also a manifestation of the problems in such a transition both for those in a society who would resist and for those who would help from outside. Americans, accustomed to quick and orderly constitutional transitions, are surprised by such events. They should not be. What is happening now in the Soviet Union, in Eastern Europe, and in parts of Africa and Latin America is far more profound; a transformation, not only of government, but of society is taking place. Strong internal resistance to reform is to be expected and comes from many quarters. Privileged groups - whether of party, race, family, or military - not only resist the loss of status; in many cases they genuinely, and perhaps with good reason, fear reprisals. Such groups, especially in the context of a communist party, believe deeply in an ideology and, as recent reporting from Cuba has suggested, find allies in those among the peasantry who feel their lot has been improved. The old guard, deeply ange red and disturbed by change and blind to the deficiencies of the old system, resent what they see as the reversal of their revolution. In the case of the Soviet Union, they play on the uncertainty that accompanies the transformation in economics and politics and find support among those fearful of the breakdown of order. Those guiding reform face the dilemma of working within the existing structure or sweeping it away. Mikhail Gorbachev had tried to work within the party and security structure. Whether he continued to believe in the doctrine or was fearful of the consequences of destroying the framework of the past is still not clear. Whatever his motives, as with those who have made similar attempts elsewhere, Gorbachev encountered the antagonism of powerful elements opposed to new thinking. Some in his circle undoubtedly proposed only cosmetic steps to appease pressures from within and without. Others fiercely resisted change. These included leading members of the structure on which he depended, and they turned on him. This can happen in any area of reform. President F. W. de Klerk of South Africa, faced with violent protests from t he Afrikaner right, must see echoes of his own problems as he watches events in Russia. Leaders of reform in many nations cry out to the democracies for support. Both governments and nonofficial bodies in the United States and Western Europe are eager to help. But no outsider is sufficiently knowledgeable about the political and social currents of another society to be fully influential. Further, such help is inevitably limited as Western leaders balance prudence with the need to respond to the political pressures on them, both internal and external. Military options are unrealistic; the strong coalition that won the Gulf war hesitated for many reasons to march on Baghdad and replace Saddam Hussein. Rhetoric from those abroad can breed false hopes of dramatic interventions. Too active a role by outside elements awakens nationalistic sensitivities and resentments against external interference that can backfire on reform. President Bush has clearly been apprehensive of generating threats to wider interests through creating instability by too active an American role on behalf of reforms, whether in the Middle East or in the Baltic states. And in the Middle East, Arab reformers hesitate - because of Israel - to be too closely identified with Washington's efforts. But the momentum of reform, spurred by today's incredibly rapid communications, continues. Even if a dramatic failure - perhaps temporary - was registered in China, successes, however fragile, have been achieved in Argentina, Paraguay, Chile, Mali, Algeria, Poland, Hungary, and Czechoslovakia. In other countries, such as Zaire and the Malagasy Republic, authoritarian leaders are desperately seeking to finesse the pressures. The forces that turned on Gorbachev remain alive in Bulgaria, Albania, and in par ts of Yugoslavia. The proponents of democracy throughout the world hail these successes and the courageous stand of those who reversed events in Moscow. These developments demonstrate that when people are effectively mobilized in today's open world, even the most formidable of old guard elements can be turned back. But the events also demonstrate that the transformation of societies is a complex process with serious risks for those involved. Those watching and supporting this global momentum should not be surprised if there are more surprises.