I don't work with those CMSs, so I wouldn't ask you to hire me as an expert in them. I would also suggest that you try to find a local person, who you can visit in person a few times to discuss what you want and monitor progress on it. You probably don't want to fly all the way to New York for that!
As for actually finding someone, you might try taking a look at local Web design firms that advertise their services, and discuss what experience they've had in doing this kind of thing. Look at their portfolio of work they've done. You might also go on to discussion boards for those three CMSs and seeing what people say about various firms, if you can't find someone suitable locally, and need to work remotely with someone. Finally, if you find a site that looks and feels similar to what you want, see if there is a link on it to the designer (also look in the Home Page code, with View Source or the like, for the designer/implementer in the comments).
It doesn't have to be a CMS, but in the long run that might be the cleanest method. It would allow you to most easily add a blog and other such content in the future. It could also be done with a straight ecommerce platform (osCommerce, Zen Cart, etc.) with a few custom pages added, if most of your site is as a gallery/sales tool. Finally, another option is to just fix up the current system to improve its look and feel, and perhaps transfer it to a Linux server (and using MySQL). Do you happen to know what language it's written in, if it's a custom project, or if not, what platform or CMS was used? I see references to some sort of "template", and DreamWeaver file types. If this was hard coded directly in HTML (DreamWeaver), it certainly should be redone in a language such as PHP (or put into a CMS). No site this size and complexity should be fixed HTML code and fixed pages.
I also see that there seem to be two nearly identical copies of the Home Page stuck together, which could be another reason why your search ranking has dropped (poorly formed page and duplicate content).