I have not had the problem, but know that it is common. In fact, go to any MB dealer at any time, and you will see MLs in the lot with the c-pillar covers held on with masking tape letting the glue dry.

I know parts are availible, and if I recall correctly, they cost different amounts for different sides for some reason.

I do not think you can "repaint and be happy" as the plastic is clearcoated with some sort of non-paint coating. You could try and sand them down and re-coat them, but it may just be cheaper to yank 'em off and replace them.