You can run through the wizard with authorize.net local checkout without express checkout. Then just remove the local checkout server behavior on the confirm page and update the redirect on the store cart details in database to go to the success page.
I wouldn't recommend storing credit card information since it is a real security concern keeping private data like that on record. Maybe just take their contact information and call them for credit card information after you have checked inventory and are ready to process it. We don't offer a secure way of storing and using credit cards offline like that.