Need a price quote engine
Receiving requests

With webform, you can create forms that allow you, or your site-admins, to create and maintain the form that site-visitors will fill out. When the form gets submitted, you can use Rules to send this information on as an e-mail. The module Webform Rules, provides the bridge between the two modules, allowing Rules to react to webform events.

Answering requests

Just turn the whole process around. Again, use webform to create a form for the request reciever to fill out. When this form gets submitted, send a mail to the requestee with the reply.

Custom work

You will most likely need to do some amount of custom coding to make this whole thing work. For example, in the mail to the sales rep, a link must be autogenerated to a form that gets prefilled with the requestee's e-mail. Auto-filling the form is likely best done as a hook_form_alter. There is a lenghty Rules video series that you can view to learn more about how to work with Rules and how to extend it to do what you need.