Okay, it sounds like you know a little bit about VNC. Here's my issue - I can VNC to the PC from my Mac by running an app called "Chicken of the VNC".
HOWEVER - that's with my desktop Mac using a wireless access point. It works like a charm and is really simple. I HAVEN'T been able to connect to my Car PC because it doesn't have an access point. It just has a wireless card. I've tried putting it in ad-hoc mode and I've used the built in airport on the Mini to set up a network. The PC sees it and even can connect to it, but if I try connecting the Mac to the PC, I get nowhere.
As for the Griffin, I don't actually know the answer to that. I've got it hooked up to my Mini in the car and the P1900 wakes and sleeps the Mini. I've never actually tried to wake the Mini before starting the car. I'll try it tomorrow morning.