How do you remove the lower right corner joint on the windshield (that black plastic thing that borders the windshield)? I need to remove it so that I can take care of a small patch of bad rust. I tried to pull it, but I am worried about breaking it. Is it just glued in? If I end up breaking it, is it expensive to replace? BTW, this is for my 87 coupe.

I don't know about re-placing it, but I do know that it's glued in with the pollyurithane that holds the windsheild in place. Mine came out real eazy, but every car is diferent.

You can always cut it off with a serrated knife and reapply it with urethane glue - just surface apply it.

So if I remove it, will the windshield leak?

What, I believe, you are talking about is the corner trim on your windshield. It "connects" the side and bottom trim pieces together. It is merely a "L" shaped piece of plastic with a little leg on the back side that clips around the shield and sits in the urethane. If you remove it and it didn't leak before, it shouldn't leak after. To ensure it doesn't, put more urethane in before you replace it. Glue it down well.