Geia hara hioniam
As I said, I never had problems with greek pdfs, because they usually have the font embedded. If they don't, I think you can do it yourself (search this forum for help, if you don't know how). The font that the prs-600 uses does display most of the greek characters, but has a problem with errr... tonous (oh yes, accents!), so the title might appear a bit strange, but the document itself will be fine.
I know it's much cheaper in the USA but I have never ordered anything from there out of fear of the possible custom charges. I think they don't hold every package, but if they do, you might end up paying the same or more as if you bought in europe (no idea exactly what the charge might be), plus lose a lot of time and peace of mind, going to get your package from the airport and so forth. Again, I have no personal experience with any of this, it's just things I've heard from friends. I personally thought it was ok to pay a little (or considerably...) more and have my reader at once, hassle-free and with no surprise costs.