I need help integrating an API between EPOSNOW system and WOOCOMMERCE (Wordpress)

General information for the website: Children's Clothing Boutique
Description of requirements/features: The API integration will allow all shop transactions to speak directly with the website in order to manage stock accurately.

I do not have the back end development experience required to set up this API but from ready the links below it seems pretty straight forward to someone with experience.
Extra notes: I have not build the Wordpress website yet, i need to factor in all costs which included this integration before I can quote.

More details on how to integrate can be found here -

https://support.modernretail.com/hc/en-us/articles/215792438-Epos-Now-WooCommerce-Integration

https://support.modernretail.com/hc/en-us/articles/204597777-POS-ERP-Integration-Overview

https://support.modernretail.com/hc/en-us/articles/210273657-WooCommerce-Integrator-Overview

Developer Section - https://developer.eposnowhq.com/Setup/APISetup