Chris,
Hi. First the next version of Dynamic Forms will have a direct integration with Paypal/Authorizenet which might help you more. For this its not very difficult to do, you can set the short field names of fields to be the required variables for Paypal and so forth. Basically you are going to have the redirect page set to paypal and then set each parameter to be passed. Within each field there under advanced setting there is a field 'Pass question to querystring variable'. You want to set this up.
The link you would specify to be the redirected to would be something like:
&business=info@datasprings.com&item_name=$(MyProduct)&amount=$(MyTotal)&no_shipping=2&no_note=1¤cy_code=USD&lc=US&bn=PP-BuyNowBF&charset=UTF-8
etc...
You might also check out this forum demonstration (although its a bit complicated for whats actually going on it does work).
Paypal Integration Example
-Chad