RS232 eTouch touchscreen

I got an ARM9 board running Linux 2.6 MontaVista. The board is running
SimpleWidget GUI software to give a simple UI interface on a eTouch
touchscreen panel. If I want to enable users to interact with the GUI
via the touchscreen, how do I integrate the touchscreen X,Y touch data
with the SimpleWidget GUI software? Or do I need to write user level
code to read in the X,Y data via serial port and then somehow resolve
the coordiates between the touchscreen and the SimpleWidget GUI and
then call the necessary routines to update the screen based upon the
users' actions?

The touchpanel sends down 5 bytes of data when the user touches and
untouches the panel. It contains X and Y coordinates of the touch.

Do I need to calibrate the screen if our screen is always the same
size, since it is an embedded product?

Any input would be appreciated....