At exactly 5,000 miles my HH displayed "Maintenance Required" above my odometer. I have appointment to change the oil, but in the meantime, does anyone know how to get rid of the message?

The dealer will reset it as part of the oil change. On my Prius (Your HH may be similar):

1 - set the Odometer on ODO - not trip
2 - Shut down
3 - Restart while holding in the ODO button and wait till the display stops changing

you have reset the 5,000 mile reminder (till another 5,000 miles goes by)

Thanks - I'll give it a try later today.