I've been having issues getting the PIC to do anything. I tried a bunch of different things, even attempting to just make an LED blink, and... nothing.
So, last night I realized I had an Arduino Nano clone sitting around, and I decided to give that a shot instead. Works great! But I still couldn't get the HPDL2416 (the LED display) to actually display anything, so now I've switched to a different one I had bought a while back. (a LEDtech LN5674-11-M1) Now I actually have it displaying one digit that counts up from 0 to 9 and then loops!
Next step will be to make it display a full 4-digit number (or maybe 3-digit with "C"/"F" after it), and then hook up the encoder... which reminds me: apparently my rotary encoder is also broken - it only gives me a signal out of one of the A/B pins. So I may have to wait for the new one to come in.
I wonder what happened to break all my components... maybe moving across the country, and then moving again a year later.