Got a display working. Some hair pulling before I realized I wired the data bus backwards. Sorry for the poorly focused image; my phone couldn't get the OLED in focus. And I still have to wire for DP and HV. dB and REL actually use the DP signal, so it's just coding. Also wiring for the mode and range switches...that's nice to have on the display.
And, no, this isn't the final solution; that display is way too small. I might go for a TFT that fits into the case opening. And then I can add cool stuff like MIN/MAX, trend plots, and data logging. Would be nice if those TFT's came with I2C interface. Using a 28-pin PIC doesn't leave many pins left.
I deserve a chai and a cookie now...