transmission slipping. early stage. will run, but dont want to take a chance. 2000 honda odyssey

How many miles on it? When was last Fluid drain & fill (WITH HONDA ATF)? While driving , has the 'D' light ever been flashing? Is the check engine light on?

Slippage is usually caused by dirty transmission screen. Buy the screen kit for your car..make sure gasket is with it..remove all bolts around edge of trans pan..about 16 + of them..carefully lower the pan..it will be full of fluid. You should see the screen. It may be held with a small screw otherwise it should pull right off of there..put new screen on..clean pan replace the gasket on the pan side and use gasket sealer..align up and put bolts back alternating tightening sequence..side to side until all are snug..then tighten but not too tight. Fill with trans fluid..good luck