Ecommerce webdesign design for my client

I have the requirement to design an eCommerce website for my [login to view URL] website will have an admin console and a webfront.I have search alot of Free Opensource but have difficulty choosing and dont have the time to [login to view URL] worker will also help in given instructions or guiding on installation and [login to view URL] are some custom features that will be required like customer who cannot make payment using the payment gateway can generate a TRANSACTIONID which concatenates DATE&SERIAL&NAMEPREFIX that can be referenced on Bank Deposits.I will also like if data can be uploaded from an existing MSACCESS Database .The worker must have verifiable reference of previous jobs.I need this quick and simple.