I hired a developer through odesk/upwork , he was based in Ukraine and cost $20usd / hr. The whole project was around $700 cad
Very professional service and I loved the hands-on chat, messaging and reporting features of upwork to keep tabs on what was being worked on and keeping track of his timesheets. If anyone needs small jobs or tweaks done to websites, or complete overhauls, upwork is a great resource.
Anyways, we did it with keeping the old site online. We did a fresh install of the latest Zencart, imported the old database. Added a few paid modules like the responsive template, our developer coded some other features we needed like the gallery and connecting the site to wordpress for a blog/news section. Once it was all set to go, we only needed to update the customer/order tables in the database and change the domain pointer to the new host. It was pretty seamless.
Before this happened, we had a few dead ends involved wasting money on a few other shopping carts, Prestashop was uselss w/ few features and very expensive modules. We also wasted time trying out Opencart, $600 on buggy modules and we paid a "developer" from their forums to import the zencart database for $100, which he failed to do. In the end, we scrapped trying open cart since by default it comes with very few features. We paid for a few dozen modules, which ended up being buggy. When we requested the module developers to help fix problems, they'd often end up fixing their module by changing core files which would then break other modules. It was a mess of code by a dozen different people and nothing ended up working the way it should. I'd advise against Open Cart, and stick to Zencart + a responsive template.