Custom eCommerce redesign

Hi,
I have been searching for a custom ecommerce programmer, (coder.) However, most of the firms or individuals tend to use templates instead of programming skills. I have researched thousands of firms and individuals on the net. However, I am not comfortable with what I found out. My question is: Where can one find out detailed information about site programmers’s credentials?
P.S
Just need to change and modify some parts of my eCommerce site.
Thanks,
Yoadber