It is not a hard job, if you have the manual, it will have a detailed description of the removal. Is a pity that your crank is broken, these are supposed to have a good strong bottom end, crank failures are turning into a common thing with Kymcos. Have you priced a genuine one yet? If you do, can you let us know how much for a genuine one? You can buy aftermarket ones. The hardest part about replacing the crank is getting the correct sleeves to reassemble the cases, but if you are handy, with a bit of patience and looking around, you can usually find what you need, I was unable to get the correct tools for this job, so just made do. Good luck with it and keep us up to date with how you go. just remember, if looking for an after market one, don't forget to look for Honda Dio as well. Parts for the Dio AF18E engine will fit the ZX50, that goes for cylinders, cranks, carbs and inlets, though I have heard that the final drive gears are different.