Navigating the Metropolitan Museum of Art can be bewildering -- there is so much great stuff to see in every direction that you can feel rudderless. So it helps to have a plan. Here is a good one: Oberlin College's Allen Memorial Art Museum in Ohio, under renovation, has sent 19 of its best paintings and one sculpture to New York, where they are in permanent collection galleries along with the works they relate to at the Met. This may not sound like much on paper, but it makes for a rewarding scavenger hunt. The exhibition, ''Side by Side: Oberlin's Masterworks at the Met,'' was organized by Maryan Ainsworth, curator of European paintings at the Met, and Andria Derstine, curator of European and American art at the Allen, and Stephanie Wiles, the Allen's director. [ABSTRACT FROM PUBLISHER]