'68 FB Rear Vent Removal

So the time has finally arrived. I've saved up enough money to get my '68 painted. I'm getting all the exterior items off the car to save a few bucks in labor. This past Sunday I pulled off the interior rear quarters so I could get at the nuts for the exterior quarter panel ornament. I'd imagine to get the exterior grills off, the complete vent door assembly needs to come off from the interior. How does that assembly come off? My interior plastic panels are still in good shape, after a clean up and fresh paint, they will look brand new. On the other hand, my original grill and slide are all pitted and dull so I will probably replace those. That being the case, how do you remove the old grill from the original plastic quarter w/out destroying it and then attach the new one?

Oh, if anyone is wondering, new color is going to be Dark Highland Green. Can you say Bullitt.......:trip:

Thanks,

Not only very thin, but almost 45yrs old too.