Help with Olds Sunroof

I have a problem with my sunroof on a 2000 olds alero. Recently, during cooler mornings/evenings (55-60 deg F) the sunroof catches on opening after
moving only about 4 inches. It looks like at around that point there is a plastic piece on the track which may be causing it to hang off. In addition I believe i should regrease the entire track since there is a spot around the same location on the passenger side which has almost no grease (maybe it is catching when the temperature is low because of the lack of lubricant and viscosity vs. temp)
Does anyone have any history with this problem?
Any suggestions on what I might do?
What type of grease should I use?
What type of solvent or cleaning agent should i use to remove the existing grease and dirt/grime?
I appreciate any help provided
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