there is quit a lot of e-commece shops around you can purchase of the net. If you live in scotland,UK (not sure about in England). The Small business gateway offer free courses in e-commerce shop building.
The thing with all this is you end up with a fairly simplistic shop that in my opinion looks cheap and nasty.
E-commerce has to be treated like a sepearate business and not part of or an exstention of an exsisting business.
If you are to make your e-commerce work for you having a specialised e-commerce developer develop the shop for you would be the better option.
A secure socket layer is require but normally provided by the company that is processing your credit card transactions. Look into WorldPay for details.
Some things to remeber, if your company is relatively new there maybe a holding time on the money from the transactions. You also need to look at the new EC directives that cover e-commerce. Certain rules and regulations need to be followed. Customers have as much right on the web as they would do in the high street, to good trading standards.
Your e-commerce developer should be able to a build content management system pages using some web technology either ASP, Php or even perl. This can be secured using database and ASP.
Due to the Data Protection Act you will not ba able to store and credit card numbers, and the company you use for taking your credit card payments will not send the credit card number to your page or database anyway.
hope this helps