If you have a buyer, then there would be very little to pay the sellers agent to do. They are supposed to find the buyer, draw up the offer, and negotiate or your behalf. If you have the buyer, you should be able to figure out how to do this by using an attorney that specializes in closings. If you've bought houses before, this will be easier.
Now if a real estate agent reads this thread, you will get a different answer, one that puts money in their pockets! If you use one, they would be doing very little work and getting a lot of money! I would love to be that agent!