Congressional hearings begin Feb. 4 on a plan to offer a one-time early retirement option to 400,000 federal workers who now lack either the age or service credit to retire.

The Senate Governmental Affairs Committee has agreed to a hearing on the bill by Sen. William V. Roth (R-Del.). It would open a 90-day early retirement opportunity for federal employes, who normally must wait until they are at least 55 and have at least 30 years of service. In some cases, the Roth bill would allow longtime workers to retire as early as age 44.

Roth's plan has been on hold for two years primarily because of opposition from unions and congressional Democrats. They believe it would produce a brain-drain and impair public services. The plan, sponsored in the House by Rep. Helen D. Bentley (R-Md.), would bar agencies from replacing most early retirees for three years.

The early-out bill would allow any employe within five years of meeting standard age and service requirements to retire early. Also eligible to retire would be workers who are age 50 with 20 years of service; age 55 with 15 years; 57 with 5 years or anyone with 25 years of service. Benefits would drop 2 percent for each year the retiree was under age 55.AMC Early Out?

The Army Materiel Command is planning a series of belt-tightening actions that include a partial hiring freeze, layoffs of nonessential temporary workers and early retirement for many senior employes.

AMC is one of the major components of the Army. The command has 110,000 civilian workers, including about 4,500 here, mostly in Alexandria and at its laboratory facility in Adelphi.

All of the actions could be canceled if Congress and the White House come up with a budget alternative by mid-December. Other Defense Department units have frozen hiring pending the outcome of the budget proceedings.

Under the hiring freeze, AMC can replace one employe for every two who leave.

The early-out must be approved by the Office of Personnel Management. Under current law, OPM can allow agencies to temporarily relax normal age-service requirements for retirement if it determines that the agency is undergoing a major reduction-in-force or reorganization that would otherwise require firing younger workers with less seniority. Fewer than half the the early-out requests OPM receives are approved, and the early-outs can be limited to specific jobs, grades and geographic areas.Health Plan Deadline

The health insurance shopping season for federal workers ends Friday. Employes who don't make any changes by the deadline will continue their current health plan next year.

Retirees who have requested additional information from the Office of Personnel Management or who didn't get the forms necessary to make a health plan selection or change will get an automatic 30-day extension from the date OPM mails the information to them.

Those retirees who didn't get health plan information should write OPM at P.O. Box 4198, Iowa City, Iowa 52244. Be sure to include a civil service retirement claim number.