User registration process with external system module

Hi,

I'm looking for a true Drupal dev to develop a module for me. I have used in the past some freelance websites and have a bad experience about developers knowing PHP but not how to really build on Drupal.
As I have a complicated module to write, I need a real expert and hope I can find one here.

The registration process for visitors has to be altered with the following steps:

Step 1
- the user enters his email
- the module checks if there is already a user with that email and in that case he's invited to login instead
- otherwise the module checks if the user exists on a remote system (using the provided SOAP library)
Step 2a (case one)
- if the user exists on the remote system, he is asked for his password
- if the password is correct, the module gets back some values associated to that user
- a form displaying those values as well as some additional values added by the module is displayed to the user
- the user can change those values and fill the empty ones and submit
Step 2b (case two)
- the user doesn't exist on the remote system
- a form is displayed to the user. It is the same form as in step 2a but with 2 extra fields to select a matching password
- the user fills the form and submit it
Step 3
- the module will use a SOAP function to send the values collected to the form to the remote server via a SOAP function provided

Once this part is covered, there will be new requirements to build on top of it.
The module shall pass the Drupal module coding standard.
The module can be shared with the community with confidential values replaced with dummy ones.

Thanks