Magento based full Ecommerce website bespoke design and build

I am looking to have a comprehensive Ecommerce website built using the magento platform, the site must have certain functionality that is essential to the jewellery industry available and made easy to use.
It needs to have the standard category options for different products, i.e Engagement Rings, Wedding Rings, Eternity Rings, Earrings etc under each of these categories there then needs to be some more categories, then once the customer arrives at the product they want they need to have the ability to customise the item i.e they will need to be able to select which material their piece will be made of, 18ct White Gold, 18ct Yellow Gold or Platinum, then the size of their stone/s, colour of the stone/s and clarity too (the stone database is a XML pass through link which has a database of stones in all sizes, shapes, colours and clarities and prices, so the layout of the search's needs to be designed but the functionality comes from the other end), with each change of any one of the parameters the price of the item must change in accordance (with metal changes prices on our end must change, with stone changes the XML pass through must return price changes from the other end and be added to the total cost. The rest of the site must be able to do all actions magento offers and anything necessary for a good Ecommerce website. I hope this gives a good description of what is needed, for a similar site that has the exact functionality that is needed along with a design that is similar to what is wanted please see www.77diamonds.com you will be able to see the application that allows you to chose an exact stone to have in the ring (using the same XML pass through as we will use), select from a list the one they want and once selected the price of the stone adds to the total and a total price is given.
I will have approx 40-75 items on the site that I will supply the images for, the images need to functionality to be able to click on them to enlarge, I will need under each product a short paragraph on what the item is and includes i.e on a particular item I would like the short description of the ring underneath with the stone details included and if a different stone is selected I would like the product detail to update with the new stone detail (please see http://www.77diamonds.com/contemporary_rings.html, underneath the main image is a description, if however you select a different stone on the right hand side that description will update.

The third party XML pass through application integrated into the site, please see http://www.77diamonds.com/classic_rings.html for reference, if you see on the right hand side under find and select your diamond is an application that lets you search diamonds and then populates a list of stones underneath that change every time you change the diamond search parameters. When a stone is selected from the list it updates the ring price and when selected adds the stone and ring to the shopping cart. Please let me know if your are able to do this, I basically need everything that happens on the reference page to happen on my site.
The following instructions are technical and might require the assistance of your company programmer)

Link Plus is a pass-through XML web service. First you will have to set up the feed on ??????.com. You have to create your own search engine, which will call our XML web services with the search parameters and get back a data set with the search results.

I think I have covered everything that id important to be able to compile a bid, if however you need to ask a question, please do not hesitate.
I would also like to point out I someone in the past has taken a job on and after 5 weeks sent over the website design, which as soon as I opened the PDF ready to see my new website design I saw that it was a free Magento template download that I had seen on the Magento website with my name at the top, he didnt even bother to change the pictures to the ones I supplied or even the currency to UK pounds, so after 5 weeks wasted with him fobbing me off I am now very delayed and would like someone who is professional and will update me all the time and can start my work immediately and work on the site to complete it as soon as possible (without rushing).

I would like to thank everyone who has taken the time to read my post and look forward to working with one of you professionals.

Kind regards,

Adam