You probably need a handle puller. They're about $15.00 at a hardward store. But be prepared. Sometimes we can't get the handles off without destroying them. After the handle is off you have a stem body. It will have a stem packing or O ring that can be replaced. To replace the washers and seat you will probably require a set of deep set sockets called tub wrenches, to reach back into the wall to remove the stem body and the stem.