Here's a post from an identical year and unit as yours.
There is no park cable input. There is only an output by the outside TV mount. I strung together a few coax and using a few adapters ran an old vcr into the outside coax output and disconnected the two interior cables going from the splinter by the amplifier panel and connected those one at a time checking for signal. I marked the one connecting to the output and have a coax wall panel on rider for that so it will become an input. I removed the splitter and shorty cable and connected the other, the radio, directly to the back of the amplifier panel. So my external output will now be an input, just have to run a cable under the TT to the park cable connection