Looking for help to enable my site visitors to submit a form that will result in a creation of an invoice and having the invoice be sent out via email

Hi Zoho.
I am currently using Zoho Invoice and Zoho sites.
With Zoho invoice, I am able to enter information about my customer, issue an invoice to the customer, having the invoice sent by email from Zoho Invoce - and the email contains a payment link to paypal. All this works great without any problem.

Now, I would like to setup a form on my Zoho Site, were a site visitor would do the following:

a) Enter their contact information, add info on what they want to order.
b) Upon entering a button saying "Review before submit order", a page should show the information entered by the visitor, plus a calculation on total sum (a fixed amount added for shipping cost)
c) Upon clicking SEND, I want the following (1-3 )to happen automatically.

1) a new contact would be created in Zoho Invoice - if identical customer information already exist, creation of a new contact would be ignored.
2) a new invoice would be issued, using a predefined invoice template
3) This invoice should be sent to the visitor by using a predefined email template from Zoho invoice, where the ZOHO/paypal link should be listed.

My question to zoho is
a) is above possible to achieve by use of the API for zoho invoice?
b) above "a" possible if I use Zoho sites as a website?
c) where can I find a reliable devloper that has the programming skills required for this?

Would be very happy if you were able to answer my questions.

Best Regards,
Bjorn