Edit a payslip

I need to edit the hours worked and hourly rate on a pay slip. The amount paid is correct. I paid through electronic payment method by downloading all the employees in the pay run on 'download bank file'. I've discovered the only way I can edit it is by reversing the pay but i'm nervous about how to do it. Can someone please suggest the steps involved, including what's involved on the bank reconcilation side and how to handle the other employees in the pay run. Thank you.