Website eShop Design & Development (Most likely Magento involved)

Hey there,

I want to set up a eShop website for my cosmetics products. Company is called Colorvision you can search on Facebook.
I had an old website made by my previous web developer: http://contactlensesaus.com.au/
But he's not available at the moment.

I want to redesign my whole website layout and start from scratch. We have a new domain name for the re-launch: http://www.colorvision.com.au/ (so far it just say under construction)

I want to create a shop similar to my old one, but more elegant and professional design. What are the requirements? Do you develop using Magento or Wordpress, which one is suitable?
I do have a mock up design, but how long would it take for the Web Design? How long will Web Development take?