Editing the Payment Page?

Hi,

I would like to make some very simple editing to the payment page to make it look more professional:

1) Reduce the length of the user and password fields.

2) Find the easiest way to add images, currency convertors, etc to this particular screen. I wasn't able to add a module specific to this page because it is a page and not a menu item. Can you suggest a way to do this? Or show me a place (files/lines) to edit this page?

Thanks,

Darren