first you would need to do some research on digital compasses (what models are out there, physical size, display options, etc.), and then you would have to remove the dash and find out what kind of room is back there to install the compass to show through the opening in the bezel.

i think its a pretty complicated job, because i would bet the LCD display is shared between the clock and the blank "gear indicator" and the only thing that separates it is the dash bezel. you might be better of replacing your rearview mirror with one from Gentex.