How to Change Border Type?

Hi, i have customised the simple contact forms CSS to fit in with my websites design for me contact page. Im wondering if you could help me with a couple of issues please?

1. I want to change the border type so its not a surrounding border, i only want a a border similar to that of the compact style contact form (one which is just a line along the top with the text split inbetween the line).

2. Also im wondering if custom buttons will work with the simple contact form im using, and if i import the custom button image will the funtionality of the original submit button still be there?

3. Im also wondering how i link the contact form button to a thank you page without removing any of the submit funtionality?

4. My website is an E-commerce website and as the contacts emailing me will be customers im wondering what to put in the 'FROM' field in the form function category? (As all customers will have unique email addresses).

Thank You