Can I fix a bent blade drive shaft on mountfield/honda mower?

I accidently caught the blade of my mower on a drain cover, which stopped it dead. After restarting it, it vibrated very badly and could only be run on the slowest of speed settings. Closer inspection revealed that the shaft the blade is attached to is bent. Is this shaft the actual engine crankshaft? and if so is it possible to get it straightened or do I have to replace it? If it is tha crank it will obviously be expensive and it may be write off. Before scrapping it I would like to investigate the options. The mower is a self propelled Mountfield with a Honda 4.5Hp engine (You would think the blade would have some kind of sheer pin that would break before the shaft would bend).