Within moments of her election to Congress from Maryland last November, Helen Delich Bentley was confronted the presiding officer of a small corporation.

No sooner had the absentee ballots been counted and her victory over 11-term Democrate Clarence D. Long assured, Bentley was in the thick of the bureaucratic and managerial duties of running a congressional office. Consider events of the 75 days since her election, during which the Republican freshman has had to:

*Prepare a $447,000 annual office budget and hire a staff of 18 people (she got 1,500 applications, including one from a liberal Democratic Senate staffer who insisted he is really ''conservative'').

* Attempt to answer about 7,000 pieces of mail.

* Select a congressional office.

* Select a computer system.

* Price the cost of printing messages on 2,500 House calendars that will be given to her constituents (she says she found a printer in Baltimore who can do it for half the price charged by the House printing office).

* Sign gallery passes for visitors from her district.

* Buy secretarial chairs for visitors for the office (''I know where I can get 'em cheap.'').

* Attend a five-day issues seminar at Harvard University.

* Attend a seminar on the nuts and bolts of Congress given by the House administration committee.

* Attend a Congressional Management Foundation workshop on how to manage a congressional office.

* Figure out where the ladies' room is.

* And, spend some time with her husband.

For Bentley and 43 other new members of the House, these kinds of managerial responsibilities can have hazardous results, particularly for the idealistic newcomer to Capitol Hill who envisions a first term filled with legislative successes, prestige and a fast flow of mail to constituents.

''There is a level of expectations that can no longer be fulfilled,'' says Gary D. Serota, executive director of the Congressional Management Foundation (CMF), which helps congressmen organize and manage their offices. ''It's an information overload.''

For new House members who plunge into the 99th Congress this week, reality will be an exhausting and sobering experience. Forty percent of the freshman's staff will be gone by the end of the first year. Letters from constituents, lobbyists or interest groups will take as long as three months to answer in some of the best managed offices, according to CMF.

Every freshman will be expected to have a 100 percent (or close to it) attendance record, which means casting about 1,000 votes on a variety of bills during the next two years. At least 300 days and more than 1,500 hours will be spent in session. A large chunk of time will be devoted to committee and subcommittee hearings, many of which will be (seldom by the congressman's admission) excrutiatingly boring. At most, according to an in-house study in 1977, each congressman will have 11 minutes each day to think and reflect.

Above all, the freshman will feel intense pressure to get reelected in 1986, a time-consuming distraction from learning the legislative process.

Given these burdens, one is forced to wonder: Can a freshman in Congress accomplish that makes legislation impossible,'' Cavanaugh says. ''It's staff, personnel, finances and planning for reelection from the day after you get in. And you have to spend a lot of time on the politics of the House, which isn't substantive either. You spend all your time positioning yourself for what has increasingly become a less substantive job. The job has gotten less and less glamorous.

''The vast majority in Congress,'' Cavanaugh adds, ''are beaten down by the drudgery.''

Part of first-term pressure results from inflated expectations. With a breakdown in the seniority system during the past decade and a dissemination of power -- there are 202 ''chairmen'' among the 535 members of the House and Senate -- the freshman who arrives on Capitol Hill no longer is inclined to wait around and pay dues knowing that he will rise eventually to an appropriate position of stature.

Now the freshman measures himself by how far he can advance during the first term. Every aspect of the job -- from answering mail to getting a particular committee assignment to hiring a good staff -- will in some way reflect the newcomer's potential for stardom in the House.

Mail, above all, is a good indicator of the freshman's dilemma. From congratulatory messages to letters of introduction from lobbyists, to mass mailings from interest groups, to thousands of resumes for staff positions, the newly elected congressman is caught in an avalanche of missives. To be exact, 200 million pieces of mail were sent to Capitol Hill last year, compared to 14.6 million in 1972.

''They are all very, very anxious on the mail when they first get here because they've never seen the volumes they get here,'' says House Postmaster Robert V. Rota. ''The big thing is to answer the mail. Already they are quite far behind. And there is no way to catch up.''

More aware than in the past of the need to respond to every inquiry from every constituent, first-term congressmen usually insist that answering mail be the top priority of their staffs. But invariably, answering the mail is the first task to be shelved when a speech needs to be written, an issue researched, an amendment drafted, a constituent coddled, a hearing attended. After all, who likes answering the mail? Certainly not the administrative assistant, or the legislative director, or the press secretary or the office manager. As a result, much of the first term is a futile race to catch up on letter.

''We're answering it as fast as we can,'' says Bentley, whose office still hasn't received large-size congressional envelopes with her signature and return address printed on them. ''It's been rough.''

Coping successfully with the mail suggests that, even if the congressman is not trained in management, he has assembled a well-organized staff capable of juggling a myriad of responsibilities. Congressional consultants, such as the Congressional Management Foundation, try to impress newcomers with the notion that the freshman who meets this initial ''management challenge'' -- who in effect becomes a good corporate leader -- will be leaps ahead of his peers. This will afford time for two other valuable activities: politicking with colleagues and supporters, and learning the ropes of getting letislation passed.

Recognizing the managerial nightmare that awaits new members, the House Administration Committee, the Democratic and Republican Parties, Harvard University's Kennedy School of Government, the Congressional Management Foundation, the Congressional Research Service and assorted others now sponsor what might be termed ''crash courses'' for freshmen in Congress.

The House Administration Committee now has special orientation and training courses ranging from the workings of the legislative process to computer technology. The committee also cosponsors a five-day seminar at Harvard, shuttling new members in a government plane from Andrews Air Force Base to Boston.

The Harvard program was the brainchild of Mark Talisman, a former congressional staffer, and began in 1972 as an experiment with four congressmen who received intensive training on legislative issues as well as the nuts and bolts of Congress. Now, about 60 percent of the incoming class attends.

Confronted with a wide array of legislative issues, some congressmen have begun taking individual tutorials with staff members from the Library of Congress or research institutes and think tanks around Washington. Former Republican Rep. Alan W. Steelman of Texas, for example, earned a reputation for making and keeping weekly appointments with an economics tutor from the Library of Congress while he was on the Hill.

But for the new congressman, mastering the art of office management is only half the story. There are equal pressures outside the office that quickly besiege newly elected House members. Not the least of these is the need to get reelected.

Bentley won in 1984 on her third try from Maryland's 2nd District, and is expected to face a popular Democratic challenger, Baltimore County Executive Donald Hutchinson, in 1986. Her advisers say she will need $1 million to run a good race.

Less than a week after her narrow victory last fall she was faced with decisions that would affect her overall strategy for reelection in two years. She needed to send a letter to thank her contributors for supporting her campaign and needed to begin an immediate fund-raising effort to retire a $60,000 total campaign debt and raise money for the next campaign. A delicate question arose: Should she send one letter to her contributors and asking for more money, a tactic that risked offending some contributors but would save valuable time and begin turning the fund-raising wheels immediately? Or, should she send two separate letters spaced several weeks apart, the first to offer thanks and the second to solicit money for the next race. (She opted for two.)

In the first weeks, Bentley also had to decide whether to keep a campaign promise to open four district offices -- including one in a predominantly Jewish area and one in a blue-collar ethnic area, both of which have been Democratic strongholds that she needs to control by 1986 -- a costly proposition that would reduce the number of staffers she could have with her in the Longworth House Office Building.

Even keeping in touch with constituents is not as easy as it used to be. With a constituency an hour's drive from Washington, Bentley already has had to attend a variety of events on weekends and evenings, a practice that will continue for the next two years. Although this will help her stay in touch with voters before the 1986 election, it will also be a constant pressure, affording little time for a personal life or activities that aren't related to the job.

With more information, more federal programs, and easier access to their representatives, constituents today have heightened expectations of the services their congressmen should provide. The congressman is no longer solely a source of information and a person to be lobbied on a bill. Nowadays he is also an ombudsman between constituents and the federal government, and molding this role successfully is key to a freshman's chances of getting reelected.

Take Rep. Frederick Boucher, a second-term Virginia Democrat from the coal-producing region of Appalachia that has an abundance of senior citizens on Social Security and coal miners receiving black lung benefits. Boucher devoted nearly half his staff positions to district offices, and he says the bulk of work done by those employes during his first term was processing thousands of claims for federal benefits.

The amount of drudge work required of the congressman and his staff brings with it an inevitable letdown about the glamor of the job. ''You come in with a lot of idealism, and it's gone within no time,'' says former-congressman Cavanaugh. ''It's good that they still start with a lot of enthusiasm. They'll need it.''

Says House Postmaster Rota, who worked for a host of politicans on the Hill, including Lyndon B. Johnson: ''I don't know why anyone thinks it's a glamorous job. It's very hard work.''

As a result, stress and anxiety usually accompany the new politican to Capitol Hill, a fact not lost on older members. Personal lives routinely end up in disarray. Former Rep. Richard Ottinger (D-N.Y.) once sent a ''Dear Colleague'' letter to his peers advising them of the benefits of counseling and suggesting that his ex-wife, a psychotherapist, would be available for consultations.

Perhaps the ultimate irony of congressional pressure came last summer. Rep. Stan Parris (R-Va.) arranged a seminar on ''stress'' and urged his colleagues to attend. But Parris had to cancel the seminar because it conflicted with an important hearing of the Banking Committee, on which he serves.

''To maintain a marriage or a family during the first term,'' says Talisman, ''is an absolute miracle.''