sun roof leak....

[EightEight50gt]

i got an 88 gt with factory sunroof. it started leaking bad this week so i removed the plastic cover things in the front, and found that the screw that goes thru the glass part was very rusted, on both sides. i got some pb blaster trying to losen the rust but no good so far. just wondering if its even supposed to come off since when i turn it, the little black disc that connects to the screw and actually holds the glass down just turns with the screw. im guessing that the screw is rusted in there and is just spinning the black thing with it. ive tried a lot of stuff and my hands hurt, just wondering if anyone else had this problem and how they fixed it. thank you