How to customize Dunning letters for the wizard and P&D?

The layouts provided by SAP don't involve any parameters at all which is interesting...I am relatively new to P&D and I know that I can map parameters in "Report Definition" but I can't get any basic reports to launch from a print preview in the Dunning Wizard. I tried mapping an out-of-the-box Crystal Report that involves no parameters and that doesn't launch either. With the "no parameters" report I get a Crystal Reports runtime error and with an invoice report attached, I get a generic Boyum popup guiding me through various troubleshooting steps but my main disconnect is "what parameters should my report require to work through the Dunning Wizard and P&D."

I'm also curious if it's possible to have different email templates for the different dunning levels, or if I have to stick with Crystal Reports.