Metro will open five new stations and more than 7 miles of track Monday morning when the new Orange Line starts carrying paying customers from Prince George's County and District of Columbia officials are planning to have employes at each of the five new stations to assist first-time patrons with such puzzling matters as how to get where you want to go and the Farecard machines.

The system will open for customers at 6 a.m. and close at midnight. It runs from 8 a.m. to midnight on Saturdays. There is no subway service on Sunday.

The opening in Prince George's County means that Metro has now reached every major jurisdiction in the area except Alexandria and Fairfax County. A total of 31 miles of subway and 29 stations are in operation. Although it is impossible to separate out all Metro construction costs and assign them precisley, Metro engineers estimate that about $1.8 billion has been spent to reach this point.

The New Carrollton line is the first Metro segment to reach as far as the Beltway, and Metro has built about 4,000 parking places at the five new stations to attract commuters. The biggest lot, with 1,900 spaces, is at the New Carrollton station itself.

In two weeks, on Dec. 3, Metro will revise about 45 bus schedules to tie most of the bus routes into the live new stations and to eliminate much of the parallel bus and subway service.