Magento – Add a custom field in Review form to collect Email Id for Guest Customers

I am looking forward to create a custom module which adds an input field to collect ‘Email Id’ in Review form but only for Guest Customers.

I know this probably needs rewriting some of the core modules like ‘/code/core/Mage/Review/Model/Mysql4/Review/Product/Collection.php’ and ‘/code/core/Mage/Review/Model/Mysql4/Review.php’ and editing block files and .phtml files to include the ‘email’ text field.

Also the new field needs to be added to the database table as well. And this field should compulsorily be there for the Guest Customers. Registered Customers need not enter their email id while posting a Review.

So I don’t know how to go about doing the following things:

1)Which core files needs to be rewritten exactly ?

2)How should I go about adding this new field in the existing database table for ‘review’ such that future upgrades don’t over write it ?

3)How should I make sure that this field is mandatorily filled by Guest Customers? (Its ok if registered customers don’t fill it)

Please, any help is massively appreciated. Thanks.