Adding functionality to a Drupal website

We have a website - [login to view URL] - which offers students Moodle hosted courses which they buy via an integrated Drupal front end. Our courses are offered by independent finance trainers. We want those students (and those students only) who buy a course from a tutor to be able to make a single comment on that tutor via a comment box and give that tutor (only) a 1 - 5 star rating, both collected via that students account. We want the student to be able to do this only once per product they buy from their our site, and within three months of buying that product. Such comments would be editable by the student up to the expiry date. We want the tutor (and admin) to be notified when a comment is posted or updated. We want these comments to display on an editable (by admin) dynamically updated tutor comment page 24 hours after they are updated on the students account. This page can be created manually when we add a tutor to our site - although we'd need instructions for how this is done. For each comment the associated rating should be shown. At the top of the page we want a calculation of the simple average star rating for that tutor. We'd like to remind any student who have not completed a comment within 7 days of the expiry of their comment opportunity period to post a comment by sending them a single email 7 days before the end of the expiry period.