Create an online store based on Magento (1839720)

We want to create an online store based on magento like the shops [login to view URL] and canvasmegastore.com. We want to sell only collections and accessories about these shop. There should be a possibility for the users to give a rating about the products and also the option to write a comment. Pls let us know, if you ever have made a similar project. If not, pls explain, how you would approach it. Pls tell us, how much time do you need for the implementation of the projekt.