how to build an e-commerce site for my retouching business?

[J]

if your current site is self hosted, there are lots of free shopping carts- payment gateways that can be used, just depends on whether your site is a CMS platform or hard coded.

if you feel your skill set is too low to build it, or you don't have the time, find an online business developer that you trust and allow them to guide you in your project

if you want to give it your own shot, either learn to code (hard coded site) or use a CMS platform with a quality OOP theme that has the design, layout and function that mastches your ideas

after it is built, you can hire someone on a PT contract to take care of it. eg: I have a friend that does not know or want to learn coding for his ecommerce site, so I wrote a small php testimonial program for him that sends the testimonials to him by email. everytime he has 10 he sends them to me to put online which keeps his site somewhat fresh