Customization Booking Script (new product type "booking on request")

I have installed a ready custom Magento script (Apptha Airhotels) on [login to view URL] and need some further customizations: Clients can book properties and must pay deposit and booking fee in advance by onestep-checkout (already installed). The script provides a new product type ('property registration“) for listing rooms and properties. Clients can choose a date and make a booking if date is available. Because some owners list their unusual properties on several booking portals, we want provide a possibility for owners to set their property to „booking on request“. For clients it should be the same procedure as for booking normal 'property registration' until checkout process. They choose a date, come to onestepcheckout-mask, fill out adress and choose one of the payment options. But on the 'Place order now“ button is now to be the note: "Clicking on 'Place order now' triggers a binding booking request if chosen date is available“. When the user clicks the button, system should send automatically a message in the inbox (message system is already provided by the Magento script) and also notification message to the host email id. The host should be able to view the details in the inbox section and to give approve or decline the request. If approved the vice verse message will send to the guest who has requested, and now the user can finish the booking by using a link in the approval message that takes him to the originally selected payment method. So your work consists in several steps: - create a new product type 'property on request' based on the existing 'property registration' with the following changings in checkout: automatically email to the host email id with the booking request (date of arrival/date of departure, property name and number of people) with possibility to approve or to decline the booking request - Information for client, that booking request is sent to the property host (on website, in message inbox and by email (to client AND admin) if booking request will be declined: email to clients email and inbox message with Information that chosen date is not available and booking is automatically canceled. Booking status changes from „pending“ to canceled - if booking request will be approved: email to clients email and inbox message with Information that request is approved by the host and prepayment or deposit must be made now by clicking a link in the mail that takes the client to the payment step of checkout, where he can make the payment as in onstepcheckout provided. The work was already done two years before, but for an earlier version of the script. I will provide it for you, so it may perhaps facilitate your customization work. Please tell me at the end, what files you've edited!