D.C. Mayor Marion Barry yesterday set Jan. 30 as the opening day for the city's long-awaited statehood constitutional convention.

Forty-five delegates elected last Nov. 3 will convene at 1:30 p.m. at Dunbar Senior High School to begin what may prove to be the laborious task of drafting the city's first constitution. It will be the fundamental document under which the 68-square-mile District and its 637,651 people would function if it should become a state.

Statehood will come only if both city residents and Congress vote approval of the constitution. That prospect could be years away.

For the moment, the statehood delegates elected at ward levels and citywide in November will begin hammering out specific language of a constitution, parceling the work among various committees and forming factions on various issues.

The City Council law creating the convention calls for the delegates to complete their work in 90 days on a $150,000 budget. Both the time and the amount of money, however, are already being questioned as inadequate by some delegates, and efforts to increase both are expected.

Barry is scheduled to convene the delegates at Dunbar, located at First and N streets NW. He will then step aside and has proposed that the delegates spend the next two weeks organizing the convention, electing officers and creating committees.

Though exact locations for the convention meetings have not been determined, Barry has offered eight rooms and the auditorium at Garrison Elementary School at 12th and S streets NW. The auditorium would be available only during nonschool hours. It was understood that some space has also been reserved at the University of the District of Columbia's Van Ness campus for convention committee sessions.

The delegates--a diverse gathering of white-collar professionals, community activists, gays, political conservatives and radicals--will be balancing their varied ideas about taxation, executive power, fiscal policy and the courts in the proposed constitution against the political reality of trying to receive approval from city voters and Congress.

Many delegates acknowledge there is likely to be resistance in Congress to the idea of allowing a small, urbanized enclave that is heavily black and Democratic to become a state equal in stature with others that are geographically much larger and demographically more diverse.

City Councilman David A. Clarke (D-Ward 1), one of three council members elected as delegates to the convention, said yesterday he hopes the scheduled 90-day convention can be lengthened, not only because of the "immensity of the task" of writing the constitution but also because of the "propitiousness of getting it through the Congress and the public."

Several other delegates have said they are counting on the current, conservative Congress becoming more liberal and hence more agreeable to D.C. statehood in the next few years.

Another immediate problem facing the convention, Clarke said, is determining whether the 90-day time frame is 90 calendar days or 90 working days. The enabling legislation does not specify either, he said.

He said 90 working days would be better than 90 consecutive calendar days, but both would work a hardship on delegates, many of whom have regular jobs they cannot leave for extended periods. He said it will be difficult for many delegates to meet five days a week, for example, and a more flexible schedule should be permitted.

Also, he said, the $150,000 budget for the convention is too small. Delegates will be entitled to a $30 per diem. This, plus other expenses, will exhaust the budget, he said, especially if the convention is allowed to function beyond 90 days.

Most of the delegates have been attending informal pre-convention meetings, including sessions with political science professors to learn about procedures and substantive issues in constitution writing.