The maintenance light can be reset using the following procedure:
Put the key in the ignition but do not turn it on.
With one hand push in the button on the speedometer for the Trip/Reset and hold it in. Continue holding it in as you use your other hand to turn the key on. You do not need to start the engine, just turn it until the dash lights come on.
Continue holding the trip/reset button in and watch the maintenance required light. It should go out after about 15 seconds. when it goes out you can turn the ignition key off then release the trip/reset button. That will reset the maintenance required light.
2000 Odyssey Online Reference Owner's Manual:
https://techinfo.honda.com/rjanisis/pubs/om/OD0000/OD0000MAINIDX.pdf