WASHINGTONIANS will rejoice that the Ford's Theatre Museum is open again after a two-year remodeling. This joy may be tempered by a reminder that the place is usually aswarm with our American cousins, not to mention the foreign tourists.

The refurbishing of the museum has been masterfully done. The exhibits sparkle, and the layout allows the maximum number of visitors to move around with the fewest possible collisions.

Without seeming to do so, the museum also packs the maximum amount of information into minimum space. No other single exhibition in town tells so much about 19th-century America in a comparable area.

Even 37 zillion kids from Kansas ricocheting round the room can't drown out the reverberations of Lincoln's assassination, with its ironic minor chord of Southern patriot John Wilkes Booth having slain the post-war South's best friend.

Virtually all the familiar old pieces are back, from the fatal Deringer to the bloody sleeve, plus a much fuller account of the aftermath, particularly the prosecution of the plotters and the persecution of such bystanders as the poor doctor whose name was Mudd.

Scheduled for completion next March is a wheelchair lift system, which eventually will give the handicapped disabled access to the basement museum; meanwhile, a video is available in the theater lobby.