Inserting forms into product Info pages

Hello Fellow Zenners,

This is the first time I'm ever posting a question on the forum .. [ with so many threads all my previous questions have already been answered :)]

This one is tricky though :

My requirement:

My site is: www.unobooks.com/shop/index.php. I have a custom requirement of gathering personal information from clients, before they order a product to cart.
This information should either be emailed to me or inserted in to the database for future refrences.

What is right way of doing this?

What files do I need to start poking around to customize the products page. I would like to embed -- few input fields, radio buttons, and when user clicks save info button, it should send a mail. All this has to happen before adding the product to cart.

Any pointer in the right direction is highly appreciated. Atleast knowing the right files to look at will be great !

Thanks again,
Uno