Sales of DaimlerChrysler's Toledo-built Jeep Cherokee plummeted 17 percent through the first six months of 2000, a slide which must be attributed to the age of the sport-utility vehicle. The Cherokee is now within a fiercely competitive market sector, and is not performing Sales of the 17-year-old Cherokee -- which eventually will be replaced by a still-secret Toledo-made Jeep to be introduced next summer -- plunged 33 percent last month alone.