Jackson,
Do a Forum search and look at the Sticky threads in Before and After the hunt section. There is alot of useful information for you about the best ways to handle the process of getting your trophies back to the U.S.
As far as your question, you will not need a broker to ship your trophies, you will need one to receive them once they arrive in the nearest port of entry back here in the U.S. Your trophies or trophy parts are going to be shipped via an independent shipping company that will be chosen for you by the Taxidermist or Dip & Pack company that processes your trophies on the African side. You have the right to choose your own companies for both Dip & Pack and taxidermy services. Unfortunately, it's probably a bit late to do your own research on them if you are leaving in 2 days. Make sure that you discuss your plans for your trophies thoroughly with your outfitter and find out who they work with before you leave Africa. Many times, you may be able to tour the facility or meet a rep from the company during your hunt.
Some hunters have cleared thier own trophies without the use of a receiving agent/broker. It is possible if you have the time, resources, and logistics to do so.... Personally, I have used a receiving agent my last 4 trips and will continue to do so. It's much more convenient to have them file your paperwork, meet with the right people, and forward the trophies right to my taxidermst's studio.... It's hard to estimate the cost because the weight of each hunters trophy shipment will vary. However, a reputable broker can give you a good faith estimate based on similar past shipments. Good Luck!