Pin 18 of the PIC is now used to select between direct readout (without prescaler) and "multiply by 64" (with prescaler).
The measuring period is 1 second (not auto-ranging ;-).
There are two versions of the hex code:
ghzfm.h1
ghzfm.h2
I don't know which will suit your display. You may have to try both.
The source code is at:
ghzfm.000
Serial 9600 baud output is available at pin 17. You will need to add a TTL to RS232 level converter. A MAX232 chip works fine.