Online auction wanted

I'm looking for someone to build a site in which people can auction to buy products at less than half their retail prices or buy them at retail prices. There will be an automatic bidder for the users who participate in auctions, and payment will primarily be made via mobile money transfer (details on this later). Unlike penny auctions such as bidhere.com, quibids.com and beezid.com, item prices are set by the admin (that's me).

This will be a scalable project as there will be one auction to start with, and as the site grows the number of auctions will grow. I'm therefore looking for a longer term arrangement which will include maintenance.

I already have the home page ready as far as look and feel are concerned.

HOW IT WORKS: There’s a timer that refreshes every time someone places a bid. Assuming it is counting down 10 seconds, the countdown will go like this:
10
9
8
7
6
5
4
3
2
1
Going …
Going …
Gone!
IE, it will count down 10 seconds and then take three more to check if anybody has placed a bid in the last seconds. I want to be able to increase the time depending on how people will respond.

There will be need for a lot of automation as auctions won't run all day, every day, and the site will need to be very user friendly.

In addition, the page size will need to be adjusted to fit my Facebook page.

I intend to use a web based help desk such as zendesk.com, but I'd like the page to be intuitive, like Amazon's, as much as possible.

I will also use a web based marketing system to handle communication and promotions such ac coupons and free bids.

As much as possible, I want to use popups (modal windows) instead of redirecting users.

As much as possible, the project should be ready to go to market four weeks after kickoff.

The site and admin panel/back end should be friendly to non-tech admins. Please let me know what platform you would use to build this site.

This is roughly what the home page will look like.