Payment form with PayPal OR Send Options

Hi Guys

I’ve seen this mentioned before but the code snippets to resolve it weren’t available.
I have a form with 3 payment options – PayPal, Bank Transfer or Finance. The second two options would just lead to different Thank you pages with the relevant information. The first one would show a PayPal button.
How can I swap the form submit button with a Paypal button depending on a dropdown choice?
Is it also possible to append something to the query string, or redirect the user to a different page, based on another select field choice?
Both of these would seem to be great additions to the form logic as I’m sure many sites offer multiple payment options like.

Many thanks!