You can't feed anythng directly to the display.

You'd need circuitry to send the info in serial form into the serial port (possible use of the tuner plug [which has a TTL level serial port] is discussed in another current thread)
Another possibility might be the coming Tuner Kit from Patrick - not sure exactly what features got implemented though...

Anyway, you'd then need a program that reads the serial port and creates the suitable bitmapped images (using some font) and then get the system to pick up teh info and incorporate it into the final screen image. Don't recall how far along HiJack etc is on this front...

All in all, not a trivial project.

/Michael