Center T-Top Plate


My 87 t-top GN has rust on the plates that are underneath the tops. I know how to take off the smaller plates but what's the best way to attack the rust on the center plate? Trying to sand it while it's on the car or taking it off to do it? How do I take it off? Is it glued on?
What is a good product to put on the rusty metal underneath the plastic trim panels that holds up the edge of the headliner--plastic piece over the driver and passengers heads.
Thx for any and all replies.
If its what i call top plate there should be two screws in front two in back.Take screws out and pull up.Be careful not to pry on it will mark.I just bought a new one from g body parts stainless but having trouble getting body shop to put in.Will let you know how it works.