The only thing that surprised me this weekend more than the fact that Papa Johns were still running deliveries in crazy snow (kudos), was the fact that DNN doesn't make it easy to insert a Paypal form into DNN.
John Mitchel posted a little how-to a while ago but here in a nutshell is the solution:
Step 1. Remove the tags from your PayPal code.
Step 2. Add the following bit of code to the input button on your form:
Step 3. Add your newly edited form to an HTML module in your DNN site.
David McKillen WebStrategies Inc.