Custom Shopping Cart

Here we have a project, that we want to have started in January. The basic outline of the project is a shopping cart, a custom one, based on my design. I have designed the website and how I wish it to look, this is in photoshop, I need the photoshop images transferring to a website, all needs to be clean CSS etc that meets W3C standards. We sell CD-ROMS and eBooks, and basically this custom shopping cart needs to have a method of when somebody purchases an eBook, the ebook is instantly delivered to their email or a download link instantly delivered. The methods of payment are Paypal, and a debit/credit card facility provided by our bank, I presume they provide an online portal in which you will need to link to. The website itself is simple, and the main template and info on left and right column never change, a small bit of flash skills is needed for one flash image. Basically, I need a custom cart providing, with a few options when making order, e.g. tick box to select product options. The website needs to be coded simply so If i ever need to edit info I can, or even better a CMS if possible. There is no rush to complete project and I wish to begin in January. Please provide some info when making your bid so I know you fully understand I need a custom shopping cart etc Please ensure website design is all SEO friendly, and URL's are short and SEo friendly.