Upgrade existing website built on Zencart

Our existing website needs some upgrades. Looking for a Zencart expert who can fix and upgrade our site. Several mods have already been done and some maybe causing issues. A few things that for sure need attention, upgrade to the latest version of Zencart, we have several page and load errors that need fixing, we'd like dual currency's available and displayed on all items (US and CAD), fix our drop down menu's (they don't align correctly) install a separate manufactures page, install a proper captcha on the contact us page (the current one is causing issues and is not secure) properly optimize entire site for SEO, streamline our checkout page, install a chat option and we're open to any other suggestions on making the whole site better.