Replicate a front-end for a customer view for an online scheduling system

We are a company that offers yoga teachers that visit homes and hotels for yoga classes for individual clients.

I have set up an appointment scheduling system enabling customers to book their own appointments. We use an online scheduling system for this - the biggest one, Appointment Plus.

I have to replicate our own front-end for this system to flow with our website, lock into the Appointment Plus database and also to go to the merchant gateway of our choice (which will be Voicepay in the UK rather than use Paypal which is our only option at the moment). This is the reason for developing our own front end - not using Paypal but the payment provider of our choice.

I have the 2 API's needed and full guides for them both - one from the Appointment System and one from the Merchant Gateway (Voicepay). It is a question of just piecing them together.

I want a PHP developer to simply copy the existing customer view that is on Appointment Plus system that we have already set up, and create the links to the payment gateway. It should be quite simple for the right person as I have scoped out the job in great detail and am aware of what exactly has to be done. I have PHP experience but not quite enough for this job. I will carry on the design after the new front end has been designed - I have 18 years experience in html and web design so the design will be left to me.

The main specifics of the job are using the main App Plus API (with Get, Create and Update commands) to replicate the PHP front-end that we already have, creating a booking scheduling system based from the feeds that are already there, database set up for a post-code selector for each of our instructors (i.e., they work in certain areas, so the customer enters their post code and the applicable instructors are shown), generating a calendar view for customers to select their appointment time, a login account section (again all from the back-end which is already there), a packages section (i.e. the ability to book 12 classes and pay for them up front and then choose the dates themselves) and simple payment integration into it. The credit card payments will be hosted on the merchants website, we only have 6 products and these need to be passed over with a simple html post form.
It sounds a lot but you already have something to replicate and everything is coming from the already set up database.

It is just a question of giving us our own front-end based on what is already there!