Google Maps Website

I want a website where by the user can search the database for a specific item category. They will also have to enter their post code and optionally a radious to search within. That category will have a post code, price, title and description. When a user searches for an item in that category the item has the category icon placed on the Google map below (no page refreshes!). When they click on the item icon they will see the image/images, title, price and description and distance from the post code they entered. Each item will belong to a company, a company can add or remove items by posting xml or manage them online. A company is set up by an administrator with a username and password and contact details (may be more than one). Each search should be recorded by user and refferal links should be logged. There should also be the option to return results from a formatted xml file also instead of the database. Users should be able to register and save their favorite items from different categories.