I have zero knowledge of web-programming. A project on which I am currently working needs to go online and it needs a payment gateway. As I have some time and interest, I thought of learning some web-programming myself and making the website. My main requirements are as follows -

* Having a webpage which is dynamic. (I must be able to change it at any point of time.)
* It must have a secure payment gateway with a shopping basket/cart facility.
* I shall be able to upload image files and pdf files on it.
* Preferably open source.

Any recommendations? Is it too difficult for a newbie to build a webpage with all the facilities listed above?