I've not replaced any on your type engine but have done a lot on Cat, Detroit & IH. I normally used a tool made for the specific engine to set a new seal. Be careful not to mar the bore in the cover or the finish on the crank while removing the old seal. I used a slide hammer with a cone shaped screw bit to remove seals, drill 3 holes equally spaced around the seal then screw the bit into 1 and bump the slide hammer 2 or 3 times then move to the next hole and repeat. Keep doing this moving from hole to hole till the old seal is removed. Make sure the bore and and crank are clean and smooth. You can use a length of pipe a washer or plate with hole the crank bolt will go thru. Use this to press the new seal into place, if the harmonic balancer has a groove worn into it from the old seal you can change the depth that you push the seal so it'll seal on a new spot on it. Lube the lip of the new seal before installing harmonic balancer with EO. Getting the belts pulleys and harmonic balancer all off is the hardest part. You'll need a puller to remove the balancer, hopefully it is drilled and tapped to accept a puller, I broke one once using a 3 finger puller in the belt groove. Good luck, I hope this was of some help, doing it's easier than explaining how to.
Ron on Northern Lights II
I don't like making plans for the day because the word "premeditated" gets thrown around in the courtroom.