Ok, then... it seems my tuner module is working ok. It's putting out voltages on Level pin that make sense for a given input.

(i.e. it's maxing out while my display still shows no bars of signal.)

So if the PIC is reporting that level via serial port, something broke there.
If the receiver is reporting the signal via I2C -> RS232, something's broken there.

I'm going to solder my receiver back in more fully.

-Ben