MICCOSUKEE RESERVATION, CENTRAL EVERGLADES-- After years of bickering over how to restore the so-called River of Grass to something resembling its natural state, the Clinton Administration last month sent to Congress a proposal to spend $7.8 billion over 20 years on a Comprehensive Everglades Restoration Plan. Threatening to derail the plan, however, are concerns over funding and the science driving the massive project. Now an 11th-hour proposal to boost water flow into Everglades National Park has a Native American tribe--and some scientists--up in arms and is adding to Congress9s doubts about the plan.