The data sheet in your link indicates that the controllers are KS0073 compatible. The KS0073 appears to be an enhanced version of the HD44780. The basic instruction set is the same although some of the bits that are unused on the HD44780 do have some significance for the KS0073. The KS0073, being a newer chip, should be faster than the HD44780 so using the timing parameters for the older chip should not be a problem.
There are two controllers (hence two enable pins) on your board to handle the extra characters. You will probably find that one of the enables deals with the upper 3 or 4 lines and the other deals with the remainder.
I think that if you want to modify an existing library you should start with LiquidCrystal1 which is an update of LiquidCrystal440 which was designed for devices with two enable pins. To get a copy start here:--> http://code.google.com/p/liquidcrystal440/ and follow the Downloads link to get to the latest version.
Don