MS CRM 2011 Case Module Submission through InfoPath/SharePoint Webform

We currently use Dynamics CRM 2011 as a case management tool to support State Agencies and a custom application they use. They currently submit tickets via email to a pre-determined support email account. The emails are forwarded by the CRM email router to CRM where a custom workflow creates new cases for us based on certain information in the email such as sender, subject, etc... Upon creation the cases are also matched up to the respective customer account and duplicate detection is being used to make sure if the case already exists, that the new email is merged into the existing case instead of creating a new case.

We are looking to replace this functionality with a web enabled form (possibly InfoPath) that gets submitted to a SharePoint form library and kicks off a custom workflow in SharePoint, notifies team members/participants/stakeholders, and feeds the form field data through to CRM to create new cases while conducting the same checks for duplicates as our current solution. This web form should include field validation and should pull certain information from CRM to pre-populate form fields and drop-down menus with info such as Customer(Organization), Issue Type, etc... The form also needs to provide the ability to attach files for submission and the form should be fed through to CRM and attached to the case upon creation.