If you are going to replace the cover plate, a few well placed whacks with a hammer & chisel will split the plate.
If the crak has siezed the the top plat will be trash unless you have access to the equipment to machine out the top hole and fit a bush
Assuming you have the crank out of the engine tip it upside down , degrease then apply some hydrochloric acid ( swiming pool acid ) diluted to about 50%.
It should also take the alloy off the crank as well.
All the usual precautions , acid burns, blinds and the fumes that come off are toxic in high concentrations.
wash and neutralise the crank with some alkali ( also from a pool shop )