those would be listed in your monitor's manual, which hopefully is included with your PC, but might be downloadable from that site, or you might be able to call them and have them tell you, if the system includes phone support. (Hint, just ask about the settings, don't mention Linux, or they'll likely tell you they don't support it, and that will be it.)
I only scanned the site and didn't find monitor information, but chances are your monitor is just a rebranded model from another manufacturer. I did a google search for:
hitachi +linux +"xwindows"
I got a few hits, but I didn't read them all. The main thing to remember is to make sure you get the numbers correct, as incorrect hsync/vsync settings can mess up some monitors (better monitors will simply not accept bad settings, but these are fairly expensive, not typically included with systems like the ones hitachi offers). You might want to look for "generic" settings (svga or better, perhaps generic settings for whatever resolution you desire, 800x600 @ 60HZ or whatever, low-balling it is better than wrecking your monitor), and use those, at least to get you started and able to use xwindows and a browser, and alter them later when you get a better answer.
It's not much, but I hope it helps some.