Unlike other places in Mexico, Oaxaca won't widely accept USD - so please get Mexican pesos.
While you won't have to worry about tipping throughout the trip at meals, etc., we do encourage tips for our guides and drivers. We recommend a range below, and this is per traveler. Feel free to allocate this and give at the end of the trip; no need to tip them at the end of each day.
Guide
$8-10 USD per person, per day
Driver
$4-5 USD per person, per day