Starting this month, the federal government will hand out more than 2 million copies of a free 124-page handbook explaining the benefits of the old and new civil service retirement programs.

Between July 1 and Dec. 31, civil servants hired before 1984 (that's about 70 percent of the U.S. work force here) must decide whether to stick with the old pension plan -- the Civil Service Retirement System -- or to move into the new private sector-style Federal Employees Retirement System. Most people hired since 1984 are already covered by FERS, which provides benefits based on Social Security, a modified civil service pension and earnings from tax-deferred investments in a new thrift savings plan.

Many private firms, for fees ranging from $11 to $32, will provide computer printouts showing benefits under the two plans. We'll run an updated listing of those services this week.

Several unions and most agencies will supply similar data to employes, at low cost (in the case of most unions) or for free if from the government.

Office of Personnel Management officials in charge of the transfer program say their free booklet, plus agency counseling sessions, should be enough for most employes to decide what to do.

Yesterday's column examined benefits, and drawbacks, of the old pension plan. Today, a look at benefits offered to workers who switch to FERS:Employes covered by FERS will pay the full Social Security tax, plus a minimal amount for modified civil service benefits. Time under Social Security- covered employment will be added to Social Security time under the FERS plan. Generally speaking, employes need to have paid into Social Security for 40 quarters (10 years) to qualify for reduced benefits at age 62 or full benefits at age 65. Workers under FERS will get a modified civil service benefit equal to about 1 percent of their high-three-year average salary for each year of service. Those retiring at age 62 with at least 20 years will get 1.1 percent of their high three for each year of service. Under that formula, an employe under FERS retiring at age 55 with 30 years of service would get a civil service benefit equal to about 30 percent of salary (compared with 56.25 percent for retirees with the same age and service under CSRS). Cost-of-living adjustments for service performed under FERS do not begin until age 62. Then retirees get full increases if the rate of inflation is 2 percent or more each year. If the cost of living is up 3 percent in any given year, the FERS benefit will be 1 percentage point less than the actual COLA for that year. All employes covered by the FERS plan get an automatic 1 percent contribution from the government toward their tax-deferred thrift plan account, even if they contribute nothing. Workers who put in 5 percent or more get a 5 percent matching contribution from the government. This year FERS employes may put in up to 10 percent of salary (to a maximum of $7,000). Employes who leave FERS before retirement eligibility can take their thrift plan investment (plus the government contribution) with them and roll it over into an Individual Retirement Account or apply it to a qualified pension plan with a new employer to protect its tax-deferred status.

OPM says that FERS is especially good for workers who intend to retire from somewhere other than the government and who invest the maximum in the thrift savings option. For employes planning to make government a career, FERS may be less attractive. Workers have five months to decide which option to choose, beginning in July. For most people, the time to start planning is now.