Build custom app API for Shopify shipping

I’m working on a project for a furniture company, have designed them a new site on shopify but need to connect the shipping via API to the shipping company’s system. Their developers have given me all the API docs for this and shopify looks pretty solid for custom shipping(?). I do also generally need a developer to help me with this project with some other stuff as I’m more of a marketing guy but I can do web design a bit on shopify WP etc.

Let me know if interested and an idea of cost / time for the API for the shipping connection.

Thanks!

George