Once you have created a Product, it's easy to edit the details. However, if someone has already purchased this Product, then you cannot delete it because that would invalidate their purchase. Instead, you can simply issue them a refund if you are no longer providing the Product in question. 

Either way, editing Products is easy. Once you are in the Payments tab of any Event, select the Product view on the left, click on an Product to open the Edit Payment side panel. Here you can edit the Product parameters. Once you are done, press "Confirm" at the bottom of the side panel to close the side panel and save your changes.