John.........a crankseal doesn't require you taking apart the crankshaft or even separating the halves of the engine casing,usually.
You get both seals brand new.........dismantle the engine on the clutch side down to removing the 2-speed clutch, and keeping meticulous track of every washer,bushing and shim, you just pop the old seal out and drive the new seal in.
The other side just requires removal of the magneto and coil mounting plate(stator plate) to access the other crank seal.
When you are into the clutch side, take note of any metal shavings and look for bad parts or broken springs,etc. A shop manual would help you out here.
Unless there is up-down play in the piston rod, you don't need to replace it. When you kit it, though, you should replace the upper rod bearing probably. don-ohio (:^)