OK, so I searched google for "firefox history access" and discovered that the history is stored in a file called "history.dat" which is in the following location: "C:\Documents and Settings\<username>\Application Data\Mozilla\Firefox\<profile>\history.dat".
Another google reveals that the file is in a format called 'Mork'. I couldn't find a C# parser for this file but did find a Java one which might help: http://www.smartwerkz.com/projects/jmork/download.html
That's about all the help I'm giving you seeing as you could have managed this on your own with a bit of work.
/- Sam Judson : Wrox Technical Editor -/