Uncle Bob offers good advice. Ask the outfitter/guide to provide the names and phone numbers of local processors (usually local butcher shop), and get their prices for processing your catch, as well as lead time for them to get it back to you (you don't need financial surprises after you harvest an animal). A good processor will provide you options for packaging (steaks, chops, sausage, ground meat, etc), and will have it all packaged, labeled and blast frozen. Also, be prepared to store your catch when you get it home. A buffalo can range from 1,500# - 2,000# on the hoof, and can yield 1/2 that weight in packaged product. You will need freezer space for all of it, or have previous arrangements to share the meat when it hits your doorstep. There are non-profit organizations that will be happy to take part of your catch and use it local food pantries, but they also must be contacted BEFORE you leave for your hunt so they will be prepared to store it when it gets there.
You only have a day to get this done, so you need to hustle.