Wordpress API integration with Clicksend to send letters

Hi. I would like someone to create a form where users will write a letter to a person. This letter will need to be sent to an API for it to be printed and sent off. The API is here: [login to view URL] I presently have gravity forms and Gravity PDF to assist with this. (I don't mind a custom solution but this may make it easier for you) One other requirement is that the letter can be addressed to multiple people. And multiple letters will be created based off this. The multiple people will need to be a selectable list that's stored in a database and grabbed from it. When it grabs those people from the database, it will need to use their names as a mail merge option. So when a user writes in the text editor {{MP_NAME}} or something like that, it will fill in their name from the database. (Their addresses will also be stored in the database) This is quite a big project. I am looking for a good developer who is fluent in English and can understand what I am talking about. This could expand to be a lot of work in the future. Think of this project as a way for people to generate letters to multiple people at once, and these letters get sent to an API.