Simple Wordpress eCommerce solution to implement on a site

I am finalizing my site where is sell stuff online: [login to view URL] I need someone to set up the eCommerce solution for me. The site is on Wordpress. What needs to be done: When clicking on "order now", visitors should be taken to a page (can be split in 2 pages/steps if needed) where they will have: - to choose the options they want : 3 different sizes, 4 different styles of caption, etc (see PDFs attached) - to type the caption they want - to give delivery details - to upload their photo Price should be updated in real time. There are 3 parameters: 1 fixed price (artwork), one price depending on the size chosen, and last depending on the location (delivery). For the delivery I wish to take the data from another site (as they will be the one shipping the product) if no headache to do that, othrwise i will enter it later when the solution is in place. This has to be linked to my Paypal (merchant account). The client should receive an invoice by email once payment is complete (but I think paypal offfers this option). I need a pop up if they leave the page before completing the order (special offer, to make them stay on the site. The solution should be simple to implement, and easy to parameter (I might add more sizes and more options in the future) Ideally, the uploaded photo would arrive directly to my dropbox ([login to view URL]) but this is not compulsory. The photo and the order should be linked somehow (may be by adding a serial number to the name of the file). This is quite standard. Nothing fancy. I am OK to change some things if that makes it simpler and easier to implement. I am not looking to re-invent the wheel, only to find a simple and easy solution for a shopping cart with the parameters above. I can give temp access if you want to take a look at the site (but it is a fairly basic 1 page website on wordpress).