to remove seal on I use an old screwdriver with a hook ground in the end. Tap one side of the seal down a little bit (that raises the other side an equivalent amount. Slide the “screwdriver” between the crank and the seal then twist it 90-degrees and lever it out.
Installing the seal I use a washer that’s bigger outer diameter than the hole in the case. Gotta make sure the washer hole will fit over the crank. Barely tap the seal into the case just enough so it stays. Put washer over the seal and using a deep socket, that also fits over the crank, drive it in place with a small hammer. The washer keeps the seal from getting cattywampus, ie-crooked, in the case or too deep