The order of the parts, outside in, would be outer retainer plate, oil seal, bearing, inner bearing retainer ring. To replace the oil seal, you have to use a press with a bearing separater tool to press the bearing off of the axle. But first, the inner bearing retainer ring has to be removed by laying the axle on a vice with the retainer bushing resting on the jaws. Then strike the bearing retainer ring with a heavy chisel in 2 places. Do not cut through the retainer ring or hit the axle surface. The 2 chisel strikes on the ring should stretch it enough to allow it to come loose and slide off the axle. Then you put the axle and bearing separater plate on the press to press the bearing off. Since you're having to remove the bearing to replace the oil seal, you may as well install a new bearing while you're at it. The new bearing must be pressed back on too. So, if you don't have those tools, and most people won't, you will probably need to take your axles to an auto machine shop to do it for you.