Mikhail Gorbachev may be a new force at the head of the Kremlin hierarchy, but many of the old names and faces are likely to play a major role as he moves to consolidate his power.

Gorbachev's emergence in the number one position appears to have been decided some time ago, perhaps as part of a compromise for the transitional selection of the late Konstantin Chernenko as general secretary 13 months ago.

As his role as next-in-line became clearer during Chernenko's tenure, Gorbachev had time to prepare himself for the prospect of assuming power and to ensure the support he needs. Likewise, the older generation had time to become accustomed to the idea that someone younger would soon outrank them.

Given the smoothness and rapidity with which Gorbachev succeeded Chernenko, it appears that the arrangement was worked out to some degree of mutual satisfaction.

The Soviet political calendar gives this relatively young and untested leader the time to move cautiously, consolidating his power while preserving the balance of political interests and personalities that helped propel him to general secretary of the Communist Party at age 54.

Gorbachev has several timely opportunities to influence the makeup of the Soviet leadership and shape the course of its economy -- through the appointment of new Politburo members perhaps as early as this spring, the election of Central Committee members this fall and the adoption of the next five-year plan at the end of the year.

But in the foreseeable future, he is not likely to disturb the roles long ago carved out by the older generation on the ruling Politburo.

Soviet Foreign Minister Andrei Gromyko, who nominated Gorbachev, is certain to continue a leading role in foreign policy. The positions of other members of the old guard, such as Moscow party chief Viktor Grishin and Ukrainian party leader Vladimir Shcherbitsky, are not likely to be affected.

Gorbachev's emergence as the party's second-ranking member in the last year also gradually undercut the view that party secretary Grigori Romanov was a strong rival for the top job.

During the past year, other key groups in the Soviet leadership such as the military and the KGB, also seem to have accepted Gorbachev's ascendancy, perhaps because he was backed by the late Soviet leader Yuri Andropov who had had the support of both groups.

Unknown is how Gorbachev will actually take charge or what problems he will face. In foreign policy, for instance, the appearance of a young, active leader will at least change the style, if not substance, of Soviet diplomacy.

Gorbachev comes from a generation of Soviet leaders who on the whole are better educated than their predecessors and who have shown a greater interest and urgency in changing -- albeit at the margins -- how the Soviet Union works.

In his role as Soviet agriculture czar, Gorbachev spoke often of the need to give people reasons to work harder and more effectively, by decentralizing economic authority and improving incentives.

In charting his course now, Gorbachev is likely to reinvigorate some of the economic reforms begun by Andropov and turn to people who share his views. The timing of his succession to power could be an asset, depending on how fast he wants to test his control.

This is a year when the Soviet Union adopts its five-year economic plan which will run until 1990. It is also the year of the 27th party congress where the Soviet Communist Party, for the first time since 1961, will adopt a new program.

The courses for both the five-year plan and the party program are largely set, but there is still time for Gorbachev to make a mark.

The party congress, which had been expected to convene in November, also will give Gorbachev a chance to change the membership of the party's Central Committee, a group of 300 people who make up the core of the Soviet leadership.

Since congresses, which alone can elect Central Committee members, occur only about once in roughly every five years, Gorbachev has an unusual opportunity early in his tenure to admit new blood into the leadership circle.

More immediately, Gorbachev can make new appointments to the Politburo, thinned to 10 with the deaths of Chernenko and defense minister Dmitri Ustinov.

Although there is no set number for Politburo seats, there is widespread expectation that at least some new members will be added this spring at the regular semiannual meeting of the Central Committee.

Who is chosen and how many new members will be added will be, under Gorbachev as under other leaders, a matter of balancing regional, political and governmental interests.

For instance, Gorbachev's promotion to general secretary leaves the Politburo with only one party first secretary. If a traditional balance is to be kept, at least one new Politburo member is likely to come from the ranks of the party Secretariat.

Possible candiates are Vladimir Dolgikh, already a nonvoting Politburo member and a party secretary for energy and heavy industry. Another is Igor Ligachev, now secretary in charge of personnel and an Andropov appointee.

Another possible addition would be Viktor Chebriko, head of the KGB and currently a nonvoting member.

The more difficult personnel task for Gorbachev will be to line up people and support in the middle ranks of the government bureaucracy and party apparatus.

How he fares in the face of the natural resistance from an old guard in both establishments reluctant to part with its powers and privileges will depend on his political skills and the power he accumulates.