Congrats on the new acquisition there, look forward to seeing what the new dynamic will bring ya.
You can get a conversion tool for CS2 to bring in RAW (yes, I prefer the unnecessary capitalization there) is dependant on the camera you have. It looks like the Evolt E500 is not listed as that name but they might have it listed as the E-500 that is on the page. Link to CS2 RAW data is here:
http://www.adobe.com/products/photoshop/cameraraw.html
Basically every camera has their own file format for what is considered 'raw' data, it's not a format on it's own. Plugins are usually fairly easy to find if it's not packaged with the program you are using but you should be good in this case.
I believe you are correct about the HDR conversion from a single shot, at least to do it well, would require the extra data that the RAW info provides since the JPG output just does not have the range for splitting the spectrum.