If your Crystalfontz LCD module has an RS232 interface, then just connect it up....
If however, your Crystalfontz LCD module has a "Logic Level Serial" interface, you will need to convert the RS232 level signals to "TTL Level" of 0 to +5V. You might even need to invert the signal as well.
Best bet is to use a module with an RS232 interface...
What part number is your Crystalfontz LCD module ??