OpenCart site running on outdated version of Ubuntu 12.04

Our web developer informed me our OpenCart site is running on an outdated version of Ubuntu 12.04, and they no longer have the skills in-house to support it. The site was launched more than 8 years ago and they admitted there has not been no effort put into maintaining the site. Their comment was “each layer (application, language and OS) have drifted out of date” and recommended updating all layers to the latest versions, but they were afraid if they attempted this it might cause the site to stop working. I am looking for somebody who can (1) update the site and (2) possibly "freshen" the appearance.

The site has pricing & the order feature hidden until the person requests an account, has it approved, and then logs into the site.