You have to lift that yoke support adapter up and remove the snap ring on the underside so it will drop off. Please be very careful working on that, it isn't easy to replace the seals. There is going to be a brass adapter in where the seal is. That comes out first then there is the seal. I found a good way to get the seal out is to use a long sharp wood screw and screw it into the seal then pull it out. I'm warning you this is not going to be easy and can be very dangerous. Someone should help so you have extra hands.