Bulb replacement snags

I need to replace tail, rear side marker, and license plate bulbs on a '95 Buick LeSabre.

The license plate bulb cover (lens) appears to be held in place by two rubberized screws. But after considerable effort on all 4 screws for the two lights, none of them have loosened. There are no dents in the body to suggest that the receptacle areas for the screws have been bent out of shape, so I have no idea of how to get at the bulbs. Does anybody know what I'm missing?

Tail light: the owner's manual said the tail light bulb would pop straight out. The manual was wrong. The bulb socket requires a turn first, which I discovered after breaking the bulb away from its brass-colored base, which is now impossible to turn or pop out. Any suggestions, other than needle-nose pliers (which have so far pulled off pieces and left the base solidly in position) or Liquid Wrench? Would Liquid Wrench or other anti-corrosives compromise the bulb socket's effectiveness?

I haven't tried the rear side marker bulbs yet, but it would help to know whether they are designed to pull out or screw out.

pull out the trunk lining along the rear of the car. There should be cutouts in the metal to let you change bulbs.