It helps if you tell us what company you will be with. Different companies have different rules on the sale of owners time. Some forbid it completely while others allow a certain number of weeks to be sold. Some allow weeks to be sold only in low season.
As far as marketing the classifieds right here are a excellent tool. I am not aware of anyone using a broker to sell time. I sell my time for a fixed rate. I guess I am cheap as the same people buy my weeks year after year. The norm seems to be about 50% of rack rate for your boat. I am probably about 40%. Will send you a PM.
G