Customising Magento extension

I am building a platform based on Magento. I bought an extension which manages the booking of nights (a little bit Air BnB style) and it has to be customised in a way it manages events, therefore from a logic of days the search (and all the related fields and processes across the extension, both from the host side and the guest side) has to be adjusted to manage times (a single event at a specific time of the day instead of nights). Second requirement is a customization of the meta description which has to be generated dynamically from the content of the event: something like "Great <name of the event> hosted by <name of the host> in <name of the city> for just <price>". The third requirement.... the extension allows already every registered user (guest) to review all the hosts. It has to be implemented a query to allow guests to review hosts ONLY if they have bought an event hosted by him/her, and it has to be created the view to manage the reciprocal review (the host has to be able to review the guest, which is not currently supported in the extension). I prefer people who have already worked on Magento. A detailed document of requirements will be provided to shortlisted freelancers / agencies and it will be signed a contract with penalties in case of withdrawal from the project or delays exceeding more than the 20% the estimated deadline (as agreed before assigning the project). Established agencies preferred.