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I am sure that there is a nicer way to describe it, but I have a tool that has always been called a "two speed nose picker". Snagged a picture off the web and it is below. Just know - you are removing it. Seal won't (most likely) come out whole...
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Need to carefully clean the timing cover before you start the seal removal.
Just to keep the crud on the outside of the motor.
That little pocket where the seal fits should be spotless. You want a good seal for sure so spend a minute with your new harmonic balancer and the new seal. Wipe a little oil or something slick on the sealing surface of the balancer. Make certain that new seal fits the new balancer!
Driving the new seal in place is done gently. Dip one side into the pocket just a little then tap left-right-left. In a perfect world, a round nylon tube would be nice. Few folks have those though. A couple of pieces of wood (make a pocket on 3 sides of the seal) will work if you don't have success with the left-right gentle taps.
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Crankshaft woodruff key... Your choice. What you have looks pretty good. If you have a new one, it can be driven down on one end, then extracted with a set of side-cutters. Remember: That open hole to the oil pan is like a black hole in space! Everything close to is will get sucked in... I suggest you pack a rag in that hole before trying to remove the key...
Installing the new one should tap gently into the slot in the crankshaft.
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Installing the new balancer: There are better tools, but a longer bolt that threads into the crankshaft will pull it gently in place. A few taps with hammer and a block of 2x4 that fits on the center of the balancer (Stay Off the rubber mounted outside ring!). A real balancer installer tool has a thrust bearing so you can snug it all the way until the balancer seats in tight.
In times I didn't have access to that tool, the "longer bolt trick" will work. Use a small 3/8 inch ratchet and only put your hand on the head of the ratchet. NOT on the ratchet handle. Turn until you have 4 or 5 threads by hand, then use your small ratchet. When it gets tight, remove the ratchet, bump the socket / bolt with a block of wood and a hammer. One time - maybe two. Then try the ratchet again. You should be making slow steady progress moving the balancer onto the crankshaft.
Rinse, Lather, Repeat.
Be sure that you get the real bolt in there nice and tight. Seated all the way. It's bad if that bolt comes loose. Use a torque wrench.