Custom module: DB query form

I would like to create a form to query a DB.

The user experience will be as follows:
1) the user will start to type the name of his profession and while he types, a list of options show up in a drop down (see search box example on www.tihotels.com)
2) The user will next enter some values in other fields - part of which are optional
3) Upon submit, the request is sent to the server and calculations are performed.
4) Results are displayed (small bar chart)
5) Next to the results, a button will invite the user to save the results - which will lead to a login or registration page.
6) Once logged-in, the results and input data will be saved part of his/her profile

The server performs calculations using the input data and additional data present in the database (e.g. conversion factors) in order to return the results. Coding these calculation is part of the scope - I will provide the mathematical formulas (a simply multiplication of factors).

I have all the data in excel spreadsheets (e.g. conversion factors) - and also a first version of the data model. Data is about ~1000 rows and 10 columns - nothing really large.

Over time, I plan to offer API access to the query functionality (but API will not include the "saving to my profile" functionality).
Goal is to architect the services so that I can easily offer a multi-threaded API in the future (e.g. using http://drupal.org/project/services).

Summary of scope:
- Define database schema
- Set-up database tables
- Code computation logic to process the data
- Create front-end forms and graphical results
- Integrate results into user profile

Optional: create REST API exposed as XML or JSON