If you already have a buyer, it is possible to sell your contract wihtout a broker. Several have reported successful sales in this manner.
HOWEVER ... if I were looking for a resale, I would not seek out a private sale, since there is no benefit for the buyer at all. Because
DVC uses it's ROFR for all sales, there is effectively a floor for resale prices created by Disney and anything lower than that floor will be purchased by DVC. The seller will receive the same amount regardless, but the buyer will lose out. In addition, all of the details must be handled by the seller/buyer unlike using a professional broker who will take care of the details.
While the seller may save a few dollars by not paying a commission, the buyer has nothing to gain since a contract for the same amount can likely be found thru a resale broker.
Good luck with your decision!